Climate Change & Aspen An Update on Impacts to Guide Resiliency Planning & Stakeholder Engagement A report of the Aspen Global Change Institute Prepared for the City of Aspen 
 Climate Change & Aspen An Update on Impacts to Guide Resiliency Planning & Stakeholder Engagement A report by the Aspen Global Change Institute Prepared for the City of Aspen Prepared December 2014
 Report Authors James Arnott Lead Author Elise Osenga
 John Katzenberger Co-authors
 Copyright © 2014 Aspen Global Change Institute. All rights reserved. About AGCI AGCI is an independent Colorado non-profit founded in 1989. The mission of the Aspen Global Change Institute (AGCI) is to further the scientific understanding of Earth systems and global environmental change through collaborative research projects, interdisciplinary scientific workshops, consulting, educational programs, publications, and videos. This work of regional to global significance provides new scientific understanding of critical environmental issues such as climate change, land-use change, and biodiversity loss, while improving scientific literacy and informing decision making and policy formation. AGCI collaborates with the science research community, governmental entities, stakeholders, students, and the public to accomplish its mission. Acknowledgements We would like to express gratitude to Imtiaz Rangwala (Western Water Assessment/CIRES), Todd Sanford (University of Colorado/CIRES), and Claudia Tebaldi (Climate Central/National Center for Atmospheric Research) for their time in reviewing and providing comments on draft versions of this report. Additionally, we owe an extra measure of appreciation to Claudia for voluntarily contributing modeling data and analysis presented in Chapter 3. Ben Moyer and John Kyle at the National Weather Service in Grand Junction supported our effort to supply historical data missing from online downloads. We would also like to recognize members of the community who volunteered their time to be interviewed for this study. They are: Richard Burkley (Aspen Skiing Company), Debbie Braun (Aspen Chamber Resort Association), Steve Barwick (City of Aspen), Sharon Clarke (Roaring Fork Conservancy), Jeff Dickinson (Energy and Sustainable Design Inc. and Biospaces Inc.), Mark Fuller (Ruedi Water and Power Authority), Boots Ferguson (Holland and Hart), Bob Harris (formerly, Blazing Adventures), Jonathan Lowsky (Colorado Wildlife Science), Barry Mink, M.D. (Aspen Valley Hospital), and Gary Tennenbaum (Pitkin County). Additional stakeholders volunteered their time to review a draft version of this report, including Daryl Grob (Pitkin County Wildfire), Tom Cardamone (Snowmass Discovery), Mona Newton (CORE), Travis Elliot (City of Aspen), Chris Bendon (City of Aspen), Will Dolan (City of Aspen), Cindy Houben (Pitkin County), Steve Aitken (City of Aspen), Lee Ledesma (City of Aspen), Phil Overeynder (City of Aspen), and Heather Tattersall Lewin (Roaring Fork Conservancy). We are appreciative of the many comments that helped improve this study. Finally, we applaud the City of Aspen and its Canary Initiative for their efforts to address the challenge of climate change. Ashely Perl and her predecessor Lauren McDonell were instrumental in identifying the need for this study and supporting its execution. Contact   For questions about this report, please contact James Arnott at jamesa@agci.org. Aspen Global Change Institute 104 Midland Ave., Suite 205 Basalt, CO 82621 970-925-7376 Table  of  contents Table  of  contents  ..........................................................................................................4   List  of  figures  and  tables  ...............................................................................................6   FOREWARD  ..................................................................................................................8   PREFACE  .......................................................................................................................9   EXECUTIVE  SUMMARY   ...............................................................................................10   Seven  key  points  .......................................................................................................................................................10   Climate  change  is  a  global  challenge  requiring  local  and  global  responses    ..................................12   Aspen’s  climate  is  changing  .................................................................................................................................13   Additional  changes  are  projected  .....................................................................................................................14   Climate  impacts  could  range  from  incremental  to  transformational  ................................................15   Stakeholders  are  concerned  and  have  begun  to  prepare    ......................................................................18   Moving  forward  on  resiliency  planning  .........................................................................................................18   Roadmap  ......................................................................................................................................................................21   CHAPTER  I:  INTRODUCTION    .......................................................................................23   Rationale  for  2014  update  ...................................................................................................................................24   DeIinitions  and  concepts  ......................................................................................................................................24   Conceptualizing  climate  risk  ...............................................................................................................................26   CHAPTER  2:  HISTORICAL  OBSERVATIONS  ....................................................................28   Global  &  regional  trends  .......................................................................................................................................28   Local  observations  ..................................................................................................................................................32   Resources  for  access  to  observational  data  ..................................................................................................40   CHAPTER  3:  CLIMATE  MODELING  RESULTS    .................................................................41   Introduction  ...............................................................................................................................................................41   Emissions  still  matter    ...........................................................................................................................................43   Projected  changes  in  temperature  &  precipitation  for  western  Colorado  ......................................45   Regional  precipitation  projections  ...................................................................................................................45   Regional  temperature  and  precipitation  projection  comparisons  .....................................................49   CHAPTER  4:  SECTORAL  IMPACTS  .................................................................................50   Introduction  ...............................................................................................................................................................50   RECREATION  &  TOURISM      ..........................................................................................52   Changes  to  Aspen’s  winter-­‐based  tourism  ...................................................................................................52   Changes  to  Aspen’s  summer-­‐based  tourism  ................................................................................................54   Response  strategies  ................................................................................................................................................55   WATER  .......................................................................................................................57   Impacts  to  snowpack  and  the  water  cycle  ....................................................................................................59   Response  strategies  ................................................................................................................................................61   ECOSYSTEMS  ..............................................................................................................63   Upward  shifts  in  plant  and  animal  distributions  .......................................................................................63   Potential  for  pest  outbreaks  in  forest  ecosystems  .....................................................................................64   Risk  of  increased  forests  Iire  size  and  frequency  .......................................................................................64   Response  strategies  ................................................................................................................................................66   PUBLIC  HEALTH  &  SAFETY  ...........................................................................................69   Decreased  air  quality  .............................................................................................................................................70   Vector  borne  disease  ..............................................................................................................................................71   Response  strategies  ................................................................................................................................................72   ENERGY  ......................................................................................................................75   Electricity  supply  implications  ..........................................................................................................................75   Energy  demand  implications  ..............................................................................................................................78   Climate  risks  to  national  and  international  energy  supply  ...................................................................78   Response  strategies  ................................................................................................................................................78   INFRASTRUCTURE  &  THE  BUILT  ENVIRONMENT  ..........................................................81   Changes  to  heating  and  cooling  requirements  ............................................................................................82   Impacts  from  extreme  events  .............................................................................................................................84   Response  strategies  ................................................................................................................................................85   CHAPTER  5:  STAKEHOLDER  INTERVIEWS  .....................................................................88   Changes  observed  in  local  climate  and  associated  impacts  ..................................................................89   Current  &  future  vulnerabilities  ........................................................................................................................90   Actions  underway  ....................................................................................................................................................91   Desired  future  actions    ..........................................................................................................................................91   Constraints  .................................................................................................................................................................91   Conclusions    ...............................................................................................................................................................92   CHAPTER  6:  PRELIMINARY  GUIDANCE  FOR  RESILIENCY  PLANNING    .............................93   Motivations  for  resiliency  planning  .................................................................................................................93   Adaptation  planning  process  ..............................................................................................................................94   Types  of  response  ....................................................................................................................................................95   Criteria  for  success    .................................................................................................................................................96   Lessons  from  other  communities  .....................................................................................................................98   Stakeholder  engagement  ......................................................................................................................................99   CHAPTER  7:  CONCLUSION  .........................................................................................100   REFERENCES    ............................................................................................................102   Appendix  A   ..............................................................................................................109   Review  of  results  from  2006  Study    ..............................................................................................................109   Appendix  B  ...............................................................................................................111   Methodology  and  additional  results  from  CMIP5  modeling    .............................................................111 List  of  figures  and  tables   EXECUTIVE  SUMMARY  FIGURES  &  TABLES   Figure 1. Global observations and projections of average surface temperature…………………12 Figure 2. Frost free days in Aspen…………………………………………………………………….13 Figure 3. Adaptation planning cycle….……………………………………………………..…………19 Table 1. Summary of climate trends observed in and around Aspen…………………..…………14 Table 2. Summary of temperature projections for Western Colorado……………………………..15 Table 3. Summary of potential climate impacts to Aspen by sector……………………….………16 Table 4. Categories of response and criteria for success………………………………………..…20 MAIN  REPORT  FIGURES,  TABLES,  &  BOXES   Figure 1.1. Assessing local climate-related risk………………..…………………………………….26 Figure 2.1. Observational record of annual mean temperature……………………..……………..29 Figure 2.2. Colorado annual precipitation, 1900-2012………………..…………………………….30 Figure 2.3. Average annual temperature in Aspen by decade……………………………………..33 Figure 2.4. Observed changes in minimum temperature by season…………………….………..34 Figure 2.5. Observed changes in maximum temperature by season……………………………..35 Figure 2.6. Frost free days in Aspen…………………..…………………..……………….…………36 Figure 2.7. Annual precipitation in Aspen…………………..…………………..………….…………37 Figure 2.8. Annual snowfall in Aspen…………………..…………………..…………………………38 Figure 2.9. Annual Roaring Fork River peak flow at Glenwood Springs……………….……….…39 Figure 3.1. Scenarios of future carbon emissions and associated temperature change………..42 Figure 3.2. Observed and projected precipitation in Colorado…………………….…………….…43 Figure 3.3. Temperature projection comparisons for Colorado and Southwest region.…………47 Figure 3.4. Precipitation projection comparisons for Colorado and Southwest region…………..48 Figure 4.1. Snow water equivalent on April 1 since 1981………..…………………………………60 Figure 4.2. Incidence & extent of fires in the Roaring Fork Valley………………………..……..…65 Figure 4.3. Projected probability of presence of West Nile Virus………..………..…….…………71 Figure 4.4. City of Aspen utility electricity sources…………………………………………………..76 Figure 4.5. Electricity production and snowpack above Ruedi Reservoir…………………………77 Figure 4.6a. Projected change in heating degree days…………………………………..…………84 Figure 4.6b. Projected change in cooling degree days…………………………………….……….84 Figure 4.7a. Projected continuous dry days for Pitkin County…………..…………………………85 Figure 4.7b. Modeled heavy rain in Pitkin County…………………………………………………..85 Figure 6.1 Adaptation planning for climate risk reduction…………………..………………………96 Figure B.1. Location of CMIP5 grid cells…………………..…………………..……………………111 Figure B.2. Projected temperature change in Western Colorado region by 2030 and 2090….113 Figure B.3. Projected precipitation change in Western Colorado region by 2030 and 2090….114 Table 2.1. Summary of Aspen climate trends.…………………..……………………………………32 Table 2.2. Comparison of recent decade to 1940-1969 average…………………………………..40 Table 3.1. Projected changes in temperature & precipitation for Western Colorado…………….44 Table 4.1. Summary of potential impacts by sector…………………..……………………………..51 Table 6.1. Categories of response for climate change risk reduction………………..……………97 Table 6.2. Selected examples of climate adaptation plans.…………………………….…….…….98 Table B.1. Comparison of CMIP3 (2006 Study) to CMIP5 (2014 Study) results…….…….……112 Box 3.1. Key points from modeling results……………………………………………………..……41 Box 4.1. Recreation and tourism summary…………………..…………………..…………………..54 Box 4.2. Water summary…………………..…………………..…………………………………….…61 Box 4.3. Ecosystems summary…………………..…………………..………………………………..67 Box 4.4. Health and safety summary…………………..…………………..…………………………73 Box 4.5. Energy summary…………………..…………………..……………………………………..79 Box 4.6. Infrastructure summary…………………..…………………..………………………………86 Box 5.1. Local changes or impacts identified by stakeholders……………………………….…….89 Box 5.2. Actions identified by stakeholders already in progress……………………….…..………90 Box 5.3. Desired future actions identified by stakeholders…………………..…………….………91 Box 5.4. Timescales for planning described by stakeholders…………….…………….….………92 Box 6.1 Resiliency planning key points…………………..…………………..…………….…….…..93 FOREWARD   Climate change, a global issue with local consequences, poses a threat to Aspen’s future. Increasing temperatures reduce our snowpack, changing water cycles diminish our rivers, and elevated risks of wildfire and landslides threaten our wilderness, property and health and safety. Aspen’s City Council, both current and former, have prepared for climate change. Though we’ve enacted a number of aggressive policies, two are vital: reducing our greenhouse gas emissions - a primary driver of climate change; and establishing a resiliency plan to help us address vulnerabilities in our local economy and environment. Both are aggressive, but necessary. The following report prepared by the Aspen Global Change Institute, Climate Change & Aspen: An Update on Impacts to Guide Resiliency Planning and Stakeholder Engagement, is intended to help inform the resiliency planning effort. It updates the 2006 report and speaks to planning needs around critical areas that climate change affects, including: recreation and tourism, ecosystems, public health and safety, built environment and infrastructure, energy, and importantly, water. I hope you’ll find this report valuable, learn lessons from it and use the information to plan for a stronger, more resilient Aspen. Thank you, Steve Skadron, Mayor December 22, 2014 Aspen, Colorado 8 PREFACE   Since the City of Aspen formally adopted a Climate Action Plan in May 2007, public awareness and concern about climate change has increased, yet societal actions remain nominal relative to the enormity of the challenge. This elevates the risk of near and long-term climate impacts to people and ecosystems—both in Aspen and worldwide. Although aggressive action—globally and locally—is needed to address the root causes of climate change, local communities such as Aspen are complementing their efforts to reduce greenhouse gas emissions by also planning for the impacts arising from climate change, some portion of which are now unavoidable. President Obama acknowledged the need to prepare for the impacts of climate change in June 2013 when he pledged his administration would “partner with communities seeking help to prepare for droughts and flood, reduce the risk of wildfires,” and “make sure that cities and states assess risk under different climate scenarios so that we don’t waste money.”1 It is clear from recent history and future projections that Aspen will face many of the impacts mentioned by the President, as well as additional changes, such as Communities like Aspen can lead the heat waves, altered precipitation, and dust on snow way in planning for the impacts arising affecting mountain snowpack and the timing of runoff, from climate change, some portion of all of which could alter the economic, cultural, and which now appear unavoidable. ecological lifeblood of the Aspen community. The City of Aspen has been a leader among cities—both large and small—in acknowledging the risks associated with climate change and pursuing aggressive and measurable actions that reduce greenhouse gas emissions. While still eager to continue visionary greenhouse gas mitigation programs, the City is now also working to prepare for climate change. The following report serves as an update to an initial 2006 report by AGCI entitled, Climate Change and Aspen: An Assessment of Impacts and Potential Responses.2 We hope the following report will be a useful complement to the earlier study and that it will make an important contribution to the City’s work towards resiliency planning. Like the 2006 report, we are not intending to recommend specific actions or policies to pursue but rather offer ideas, observations, projections, and stakeholder perspectives that may be useful as a starting point in engaging the community on preparedness. 1  Obama,  Barack.  2013.  "Remarks  by  the  President  on  Climate  Change"  (speech,  Washington,  DC,  June  25,   2013),  White  House.  http://www.whitehouse.gov/the-­‐press-­‐ofIice/2013/06/25/remarks-­‐president-­‐ climate-­‐change 2  Aspen  Global  Change  Institute.  2006.  Climate  Change  and  Aspen:  An  assessment  of  impacts  and   potential  responses.  Available  at:  http://www.agci.org/dB/PDFs/Publications/2006_CCA.pdf 9 EXECUTIVE  SUMMARY   Aspen’s climate is already changing, and additional changes are anticipated throughout the 21st century and beyond. These local climate shifts will take place within the context of regional and global changes, all of which may result in conditions unprecedented in human history. The impacts of climate change are likely to affect Aspen’s residents, ecosystems, and environmental amenities as well as the home communities of Aspen visitors. For Aspen, climate change will likely include longer summertime warm periods, earlier onset of spring snowmelt, more precipitation arriving as rain rather than snow, and longer dry periods with heavier precipitation events in between. These types of changes could exacerbate already risky wildfire conditions, place extra pressure on already stretched water providers and users, provide additional challenges to ski area operators and other winter and summer recreation providers, as well as result in other impacts to every sector important to the Aspen community. Alongside the many challenges, new opportunities may also emerge, such as the possibility for expanded summertime activities. The following report considers observations, climate modeling projections, relevant research from the literature, and stakeholder perspectives to explore climate change in Aspen as a basis for resiliency planning. Based on this effort, seven key findings emerge. Seven  key  points   1. Climate change continues to be an issue of global concern with mounting evidence of current and future impacts to society and ecosystems. A consensus among decisionmakers, citizens, and scientists is steadily growing and calls for action on emissions reduction and preparedness at international, regional, and local levels. 10 2. Temperatures in Aspen during all seasons have increased since 1940, and the summertime frost free period has lengthened by over one month. Precipitation and snowfall have declined slightly since 1980, although an overall increase has been observed since 1940.3 3. Climate model results for the Aspen region project rising temperatures and alterations to precipitation over the 21st century, and a key determinant of the magnitude of these changes will be future global greenhouse gas emission levels. 4. Impacts from observational trends and future projections will affect critical sectors of the Aspen community, including water, energy, recreation and tourism, public health and safety, ecosystems, and the built environment. 5. Local stakeholders are concerned about climate change and its impacts on their environment, business, and/or personal well-being. Many of the stakeholders interviewed for this report indicate they are already taking climate change into account for current decision-making and will likely continue to do so during future planning. 6. Resiliency planning and implementation can help reduce vulnerability to anticipated impacts as well as exploit beneficial opportunities. This effort is strengthened through stakeholder engagement and involvement, ongoing monitoring and evaluation, and processes that allow for flexible response strategies as both anticipated and unanticipated changes emerge. 7. Significant reductions in greenhouse gases are a necessary part of ensuring resiliency. Efforts to plan for the impacts of climate change will be more difficult, more expensive, and less likely to succeed if near-term strategies for emissions reductions are not enacted. While ongoing efforts to reduce the root causes of climate change are still urgently needed, preparedness planning for future scenarios of climate-related impacts are also an essential component of society’s response to climate change. By pursuing resiliency planning as a strategy for preparedness, the City of Aspen continues its legacy of leadership on climate change issues. The aim of this report is to serve as an update to a previous study conducted by the Aspen Global Change Institute in 2006. The findings presented here offer an assessment of observations, modeling, climate impacts research, and interviews intended to provide a 3 In 1980, the Aspen weather station underwent a change in location, moving approximately 200 feet higher in elevation. 11 groundwork of scientific and stakeholder input to inform and support the City’s resiliency planning process. While scientific understanding has expanded and improved since the time of the 2006 study, the results of this work largely reconfirm its main conclusions. Climate  change  is  a  global  challenge  requiring  local  and  global  responses     Globally, surface air temperatures have increased 1.5ºF (0.8ºC) since 1880. Projected future increases range from slight to staggering and are primarily dependent upon future emissions. As Figure 1 illustrates, average climate model projections indicate over 7ºF (3.9ºC) in additional warming under a high emissions scenario, whereas the lowest emission scenario produces less Figure 1. Global observations and projections of average surface temperature Figure 1. Observations and climate modeling results illustrate 20th and 21st century global average temperature. For historical periods, climate models largely reproduce observed conditions. For future projections, two greenhouse gas emissions scenarios are considered: a low emissions scenario, called RCP2.6 (in blue) and a high emissions scenario called RCP8.5 (in red). End-of-century temperature projections for two middle of the road scenarios, RCP4.5 and RCP6.0, are indicated to the right of graph. Under any scenario, temperatures continue to increase beyond present day levels. Additional end-of-century results for other emissions scenarios are provided to the right. Shading indicates the range of results provided by the ensemble of models. Source: Melillo et al. 2014. 12 than 2ºF (about 1.1ºC) in additional warming. However, it is important to note that achieving the low emissions scenario would require negative emissions later this century. While both scenarios will result in climate-related impacts, the magnitude of those impacts is likely to vary greatly depending on the trajectory of actual emissions over the coming century. As of 2014, the world continues to closely track the highest emissions scenario (RCP8.5). Around the world, the impacts of climate change are already underway, affecting agriculture, human health, ecosystems on land and in the oceans, water supplies, and the livelihoods of more vulnerable populations. Future additional impacts along these lines are expected, and therefore, considering options for climate preparedness is now occurring at local, regional, national, and international levels. Aspen’s  climate  is  changing   Observations of Aspen’s climate since 1940 indicate rising temperatures and lengthening summers. Minimum temperatures have increased more than maximum temperatures, while average temperatures have increased approximately 2ºF (1.1ºC). One of the most striking indicators of Aspen’s changing climate is the trend in frost free days, where the length of the frost free period has increased by 23 days since 1980 (see Figure 2). Figure 2. Frost free days in Aspen Figure 2 shows a rise in the decadal average of consecutive frost free days since the 1940s. The final darkest green bar does not represent a full decade; it represents only the decade to date: 2010-2013. The location of Aspen’s weather monitoring station changed between 1979 and 1980, shifting upward in elevation ~200 feet. Data source: NOAA-NCDC Aspen Stations 370 and 372. 13 Trends in total precipitation as well as snowfall are mixed, both revealing an overall increase since 1940 yet a slight decrease since 1980. Analysis of local climate trends is somewhat confounded by the relocation of Aspen’s primary weather station in 1980 and the high variability associated with single station records. Table 1. Summary of climate trends observed in and around Aspen Observation Trend: 1940-1979 Trend: 1980-2013 Average Temperature 1.0º F increase (.6º C) 1.4º F increase (.8º C) Frost Free Days 11 day increase 23 day increase Total Precipitation 2.6 inch increase 0.6 inch decrease Snow Water Equivalent (Independence Pass) Data not available 1.2 inch decrease Table 1. Trends for the periods 1940-1979 and 1980-2013 are displayed based on data from Aspen’s weather station. As explained in further detail in Chapter 2, Aspen’s weather station relocated in 1980 approximately 200 feet up in elevation, which may affect the trends observed since 1940. Sources: NOAA-NCDC stations 370 and 372; NRCS SNOTEL Independence Pass. Addi`onal  changes  are  projected   Future projections of the Aspen region indicate further increases to temperature. Model projections of precipitation are more uncertain, but recent results suggest slight increases. However, due to temperature increase a greater proportion of precipitation is likely to come as rain rather than snow, with repercussions for water availability. A key uncertainty in estimating the magnitude of future changes and their impacts is the quantity of future global greenhouse gas emissions produced by the global economy. Currently, the world continues to follow a high emissions trajectory. Under this scenario (called RCP8.5), projections prepared for this report for the Western Slope region, including much of the Colorado plateau, suggest a nearly 3ºF (1.7ºC) temperature increase by 2030 and a nearly 10ºF (5.6ºC) temperature increase by 2090, relative to observations during the historical period 1980-1999. These projections are consistent with a similar analysis for the entire state of Colorado. In comparison, a switch to a middle emissions (RCP4.5) scenario could reduce projected temperature change by the end of the century by nearly half. While aggressive emissions reductions may forestall possible catastrophic changes to Aspen’s climate, there are still significant changes anticipated under assumptions of lower emissions. In other words, Aspen’s climate is projected to change even with the more optimistic emissions scenarios. As a consequence, building resilience to the impacts of climate change (i.e. 14 adaptation) is now a prudent complement to existing efforts to reduce emissions (i.e. mitigation) for all likely future pathways. Model projections of precipitation prepared for this report suggest a slight increase in total precipitation is likely for the Western Slope region during the 21st century. Conclusions drawn from a survey of other modeling results for the surrounding region published since 2006 remain Aspen’s climate is projected to change mixed. Some results lean towards greater under both low and high emissions precipitation, others less, and all results contain scenarios. Resiliency planning is uncertainty bounds that include the possibility for relevant for either pathway. either greater or less than historical amounts of precipitation. While projections of precipitation remain uncertain in terms of the overall direction of change, there is high confidence that within the given magnitude (plus or minus) of modeled precipitation projections, rising temperatures will have a drying affect on local hydrology regardless. From a planning standpoint, resource managers will need to take into account the uncertainties associated with precipitation projections. Even within these uncertainties, planning efforts can count on the relative likelihood that future precipitation will increasingly come as rain rather than snow, increased temperatures will accelerate drying, and inter-annual variability—long a condition of the Roaring Fork Valley and the broader U.S. West—will persist. Table 2. Summary of temperature projections for western Colorado Projection Period Medium Emissions (RCP 4.5) Temp. Change in Deg F (Deg C) High Emissions (RCP 8.5) Temp. Change in Deg F (Deg C) 2030 +2.8 (1.6) +2.9 (1.6) 2060 +4.5 (2.5) +6.2 (3.5) 2090 +5.3 (3.0) +9.7 (5.4) Table 2. Projections of temperature change relative to the period 1980-1999 are provided for medium (RCP4.5) and high (RCP8.5) emissions scenarios. More results are discussed in Chapter 3, and additional discussion of methods and additional results are available in Appendix B. Source: C. Tebaldi. Climate  impacts  could  range  from  incremental  to  transforma`onal   Climate change will impact a broad range of sectors vital to Aspen’s economic, ecological, and cultural well-being. For this report, impacts to recreation and tourism, water, ecosystems, energy, public health and safety, and the built environment are considered. 15 Table 3. Summary of potential climate impacts to Aspen by sector Climate-related changes Potential impacts Recreation & Tourism • Increasing wintertime temperatures • Shift toward more precipitation falling as rain • Increasing stream temperature • Changes to timing and quantity of runoff • Difficulty achieving targeted ski area conditions during existing ski season schedule • Reduction in suitable fall and early winter conditions for snowmaking • Alterations to timing of ideal summer and winter recreation conditions • Degraded aesthetic quality of environment and increasing hazards posed to visitors (e.g. fire) Water • Increasing dry periods in the Western U.S. • Decreasing proportion of precipitation falling as snow • Changes to the timing and availability of water • • • • • Ecosystems • Increasing length of frost free period • Alterations to the timing and type of precipitation • Increasing annual and seasonal temperatures • Alterations to snowpack timing, quantity, and areal coverage Public Health & Safety • More extreme high temperatures and higher average temperatures • Higher risk of extreme events (e.g., flood, drought, fire, landslide) • Air quality impairment such as increased presence of ground level ozone • Changing ranges of disease-carrying species • Changing climate conditions correlating to areas of food or water supply • Environmental-stress related mental illness • Loss of property or injury related to disaster events • Lengthened and growing allergy season • Increased respiratory illness Energy • Increasing high temperatures during summer • Warming of wintertime minimum temperatures • Alterations to snowpack and timing and quantity of runoff • Uncertainty in future dependability of hydropower resources • Increase in cooling load and reduction in heating load of building’s energy demand • Climate-related risks to national and international energy supply Infrastructure & the Built Environment • Shift in the magnitude of temperature and precipitation extremes • Warming of wintertime minimum temperatures; increase in summertime maximum temperatures • Alterations to timing and quantity of runoff • Increase in hazards to structures and infrastructure from flood, fire, landslide and drought • Increase in cooling load and reduction in heating load of buildings’ energy demand Greater pressure on existing water resources Changes to ecological regimes Increased fire risk Changes to timing and volume of peak flows Reduced hydroelectric generating potential • • • • Plant communities shift to higher elevations Local specialist species diminish or disappear Encroachment by invasive species Enhanced conditions for outbreaks of insects affecting trees • Enhanced conditions for more frequent, more intense, and larger wildfires • Alterations to water quality 16 This report draws upon local observations and regional projections, as well as relevant scientific literature, to discuss the types of potential impacts that may occur in the Aspen area. However, specific responses are beyond the scope of this report and will require more detailed investigation into location-specific risks and strategies for their reduction. One example is the need to update studies on landslide risk based on projections of future hydrologic patterns — such as the rate of snowmelt and frequency and intensity of heavy rain events. Some of the impacts identified in this study may take place gradually over decades, such as changes in energy demand patterns by people or gradual uphill shifts in plant and animal species. Other impacts, such as a severe fire or a precipitation event that causes a flooding or mudflow event could occur suddenly with dramatic and immediate consequences. Uncertainties remain in both areas, including the pace at which the global economy will decarbonize and the sensitivity of the global climate system to increasing concentrations of greenhouse gases in the atmosphere. Vulnerability to these global changes at a local level, in turn, will depend on how local climate is affected by larger regional and global patterns. In addition, site-specific conditions, such as the exposure of structures to fire or the capacity of emergency response in event of a flood, are relevant for evaluating risk and prioritizing potential response strategies. Ongoing consideration of all of the aforementioned components of local impacts assessment are needed as Aspen plans, implements, evaluates, and adjusts its response to both near and long-term impacts of climate change. 17 Stakeholders  are  concerned  and  have  begun  to  prepare     As a preliminary source of input from the Aspen community, AGCI and the City of Aspen interviewed eleven stakeholders representing the spectrum of sectors considered in this report. Interviews were designed to elicit stakeholders perspectives on climate change, such as personal observations of changes, impacts identified, actions contemplated or taken in response, and overall level of concern about climate change relative to other issues. All stakeholders surveyed were able to identify changes in the environment they found to be significant, although many were uncertain as to the extent the alterations were caused by climate change. Perceived changes identified by stakeholders included: More common drought conditions Less predictable seasonal weather patterns Earlier onset of spring Decreasing winter snowpack Reduction in extreme cold winter temperatures Species shifts in plant and animal communities • • • • • • In general, stakeholders interviewed for this study were already involved in efforts that in some way, whether or not specifically focused on climate change, relate to reducing vulnerability or enhancing resiliency. These efforts include: Watershed planning and riparian health management (i.e. Roaring Fork Watershed Plan) Enhancing operational speed and flexibility for snowmaking Mitigating wildfire hazard and wildfire response capacity Implementing greener building codes Adjusting timing, size, and location of commercial rafting trips Expanding attractions for tourists during early winter and shoulder seasons • • • • • • In addition, numerous areas of activity were identified by stakeholders for potential future actions, whether taken independently or in collaboration with other entities. These desired future actions include public education, enhanced flexibility in planning and action (e.g., development of crisis plans), reconsideration of water laws, long-term monitoring, and adjustment of building codes in relation to fire protection and energy use. Moving  forward  on  resiliency  planning   Resilience: The ability of a system and its component parts to anticipate, absorb, accommodate, or recover from the effects of a hazardous event or gradual system change in a manner timely enough to ensure the preservation, restoration, or improvement of its essential basic structures and functions.- Adapted from IPCC 2012 18 To build resilience in the face of the complex nature of climate change requires an iterative, community-based process of assessment, planning, implementation, and evaluation. While elements of this cycle have occurred in the past, this phase of Aspen’s engagement with resiliency planning represents the green circle in Figure 2. This type of process and its resulting outcomes are strengthened by engagement with a broad base of stakeholders, including those who may be impacted by actions taken as well as those who can inform and implement responses strategies. A diversity of criteria and types of responses can be considered in this process, and lessons from other communities may prove helpful in navigating the path forward. Figure 3. Adaptation planning cycle I. Learning & Assessment! IV. Evaluation! Adaptation Planning Cycle! III. Implementation & Monitoring! II. Planning & Engagement! Figure 3. Planning in the context of change is often best supported by an adaptive planning process that is cyclical rather than linear and allows for learning and adjustment along the way. Initial learning and assessment (I) informs planning and initial engagement with the community (II). Plans are then implemented and long-term monitoring based on goals and objectives (III) enable evaluation. As learning takes place within the sectors of our community — what worked, what didn’t, and why — the adaptive management cycle begins anew, building from refined goals of and approaches to resiliency and sustainability. Figure 3 presents an idealized version of the adaptive planning process as four phases. Though in practice resiliency planning may not occur as neatly as illustrated here, the notion of planning as a cyclical process instead of as a linear route with beginning and end points is a central theme of effective resiliency planning in the context of climate change. 19 As a resiliency planning process begins to contemplate actions and the goals that impel them, a range of types of response can be considered along with multiple criteria for gauging success. For example, responses to the impact of increasing wildfires could include reducing exposure of assets in fire prone areas, reducing the vulnerability of structures through best practices in wildfire mitigation, enhancing emergency response and recovery capacity, or a combination of all these approaches as well as others. Response strategies under the category of transformation may include a number of resiliency enhancing actions coordinated with efforts such as greenhouse gas reduction goals that, in combination, increase the overall sustainability of a community. Criteria for success can be considered throughout resiliency planning and can cover a broad range of factors, including the avoidance of economic losses and preservation of basic municipal services. Criteria can also extend to capture important, if harder to measure, factors such as maintaining ecological health, preserving procedural integrity, and maintaining or even enhancing community character and culture (see Table 4). Table 4. Categories of response and criteria for success Example Categories of Response • Reduce exposure:(e.g., relocate assets from high risk areas) • Enhance response and recovery preparedness (e.g., increase emergency response capacity) • Increase resilience to changing risks (e.g., planning for multiple future scenarios) • Reduce vulnerability (e.g., hardening infrastructure and services to extreme events) • Transfer and share risks (e.g., collaborative planning and action with stakeholders and neighboring governments) • Transformation (e.g., pursing an integrated approach to mitigate underlying causes of risk while also enhancing resiliency and overall sustainability) Adapted from IPCC 2012 Example Criteria for Success • Economic: Minimizing or avoiding financial losses and/or capitalizing on opportunities and benefits • Institutional: Preserving the ability of institutions, policies, and resource management to meet obligations to constituents as well as ecosystems • Ecological: preserving the resilience capacity, diversity and services made possible by healthy ecosystems • Social: Reducing vulnerabilities and/or inequities within marginalized populations while strengthening communities • Procedural: Supporting transparent and inclusive processes • Cultural: Preserving and/or enhancing vital aspects of community character and civic culture Adapted from Moser and Boykoff 2013 20 Communities large and small have begun considering and implementing actions to enhance resiliency. Examples range from Keene, New Hampshire to King County, Washington — from New York City to Moab, Utah. In many instances, exemplary plans include inclusive processes for community input, a scientific basis for considering future impacts, specific action items that delineate responsibilities, timelines, and measurable outcomes, as well as opportunities for reflection and flexibility as future conditions unfold over time. Additionally, regional and national networks and organizations have formed to provide resources to support communities in their efforts. Chapter 6 of the report offers more details and descriptions of these resources. Leadership as well as partnerships plays an important role in developing and implementing resiliency strategies. Aspen is in a position to demonstrate leadership in adaptation strategies for mountain resort communities. Roadmap   The full report examines the key points and statements made throughout this summary in greater depth. Chapter 1 outlines the rationale for the update to the 2006 report and provides a conceptual overview of assessing climate-related risk at a local scale. Definitions pertinent to thinking and communicating about preparedness for climate change are provided. Chapter 2 presents observational data on recent historical patterns of climate change for the world, the southwestern region, and for Aspen. A specific analysis of available Aspen weather data since 1940 is reported in addition to a brief discussion of historical hydrologic data on the Roaring Fork River. As a complement to historical observations, Chapter 3 looks forward by using several lines of climate modeling results to portray possible future climate conditions in the Aspen region based on various greenhouse gas emissions scenarios. One approach taken employs a similar methodology to those utilized in the 2006 Study. Another approach characterizes the results of modeling studies for regions surrounding or near to Aspen and compares these new results to the results of the 2006 Study. Chapter 4 explores the potential impacts to six sectors identified as important to the City of Aspen while setting of the scope of this study. They include: recreation and tourism, water, ecosystems, public health and safety, energy, and infrastructure and the built environment. The impacts presented in this section are based on a survey of scientific literature addressing climate-related impacts in areas comparable or related to Aspen. It is anticipated that this overview will be a launching pad for more in-depth consideration of how anticipated trends and changes will play out locally. Chapter 5 summarizes the input received from a set of eleven stakeholder interviews conducted in early 2014 by AGCI and the City of Aspen. Stakeholders were selected to represent the range of sectors examined in Chapter 4, and the interviews were intended as a preliminary round of 21 engagement with the community on climate change impacts and resiliency planning. Summaries of changes and impacts identified by stakeholders as well as actions taken or in planning are documented and discussed. Chapter 6 offers some preliminary guidance for the anticipated City and community effort on building resiliency. A conceptual model for adaptive management, categories of response that build resiliency, criteria to consider when defining goals and objectives, and a small set of helpful examples are provided. Finally, a concluding section points the way forward and identifies areas of future research that could support a resiliency planning process. Many of the climate impacts and vulnerabilities discussed in the 2006 report related to climate change impacts on the physical, socioeconomic, and ecosystems of the Aspen area have been validated in the literature on Upper Colorado River basin and mountain resort communities in general. This new study, however, shifts its focus towards resiliency and how to frame it in a changing climate as a critical complement to ongoing mitigation efforts. It serves as an introduction to areas the City and the community as a whole may consider in developing a comprehensive resiliency plan — a living document updated as conditions change and new information becomes available.
 
 22 CHAPTER  I:  INTRODUCTION  
 Aspen’s climate is already changing, and even greater change is anticipated in the future. Although future climate-related societal and ecological impacts in Aspen cannot be identified with complete certainty, they are likely to range from significant to severe and touch a broad range of sectors critical to Aspen’s economic and cultural livelihood. Preparing for potential changes in ways that enhance resiliency and reduce vulnerability to identified risks can enhance the overall sustainability, vitality, and prosperity of a community. As a result, steps taken toward resiliency planning, along with continued leadership in implementing greenhouse gas emission reductions, offer hope that Aspen’s unique environment and Aspen’s climate is changing and will very culture will continue to be deeply appreciated and likely continue to change, with important highly valued by residents and visitors alike. implications for the community’s resiliency and preparedness The following report—Climate Change and Aspen: An Update on Impacts to Guide Resiliency Planning and Stakeholder Engagement—represents a fresh assessment of science and practice relevant to the City’s commitment to climate resiliency planning. This report builds upon a study prepared for the City by AGCI in 2006 entitled: Climate Change and Aspen: An Assessment of Impacts and Potential Responses (hereafter referred to as the “2006 Study”).4 The 2006 Study was a larger effort that explored more in-depth the potential impacts of climate Aspen  Global  Change  Institute.  2006.  Climate  Change  and  Aspen:  An  assessment  of  impacts  and  potential   responses.  Available  at:  http://www.agci.org/dB/PDFs/Publications/2006_CCA.pdf 4 23 change, with a focus on snow availability for skiing and its direct and indirect effects on the local economy. This 2014 report presents a broader assessment of impacts across multiple sectors, though not in the same level of detail as applied to the specific sectors examined in 2006. A summary of results from 2006 is provided as Appendix A of this report. Ra`onale  for  2014  update   A placeholder to consider options for climate adaptation was included as part of the City of Aspen's Climate Action Plan adopted in 2007. Focused attention on this component started in 2012 as part of discussions among City staff and members of the Aspen Global Warming Alliance (AGWA). In August 2013, during a summer retreat, the Aspen City Council identified development of a climate change resiliency plan as one of its top 10 goals for the coming year.  To inform this work, the City has engaged AGCI to identify important updates in the science pertaining to climate change impacts in the Aspen area and to consider a wider range of impacts that are relevant to local resiliency plans and practices. The intention of this report is not to recommend specific actions or to be prescriptive about adaptation strategies, but rather to provide a context for dialog within the City departments, staff, and the community on building resiliency in the context of climate change. These ongoing discussions will in some cases provide the basis for further studies to provide more detailed information — for example on municipal water availability or risk to people and property from area landslides in an altered climate. Defini`ons  and  concepts   As a prelude to the chapters that follow, several useful definitions and concepts for considering the dimensions of climate-related risk at a community scale are presented. Climate variability and change – Climate refers to the average conditions of weather, such as air temperature and precipitation. Drivers of change in climate include natural variability and human contributions at global and local scales. For basic information as well as details about the scientific basis of climate science, impacts from climate change, and possible solutions, we recommend a series of reports published by the United Nations Intergovernmental Panel on Climate Change (IPCC 2013, 2014). For each of these reports, a summary for policy makers is 24 provided.5 Additionally, a U.S.-focused report—the Third National Climate Assessment— provides similar background material on climate science as well as region-by-region and sectorby-sector analysis of domestic climate change impacts.6 Vulnerability – The degree to which a system—for example, a city, business, or ecosystem—is likely to experience harm due to exposure to a hazard, either a perturbation or a stressor.7 Adaptation – Actions throughout society—by individuals, groups, and/or governments—in response to actual or expected climatic impacts, which reduce harm or exploit beneficial opportunities.8 Adaptation can be reactive to an abrupt or gradual change, or it can anticipate these changes and adjust accordingly using best available information. Resilience – The ability of a system and its component parts to anticipate, absorb, accommodate, or recover from the effects of a hazardous event or gradual systemic change, in a manner timely enough to ensure the preservation, restoration, or improvement of its essential basic structures and functions.9 Risk - The likelihood of significant alterations in the normal functioning of a community due to hazardous physical events or long term changes that lead to adverse human, material, economic, or environmental effects.10 A component of risk is existing societal capacity to absorb, cope with, or respond to hazards and impacts For the latest Intergovernmental Panel on Climate Change (IPCC) series of assessment reports go to: www.ipcc.ch. The last comprehensive assessment report produced by the IPCC was the Fifth Assessment Report (AR5) completed in 2014, which include summaries for policy makers. 6  Melillo,  Jerry  M.,  Terese  (T.C.)  Richmond,  and  Gary  W.  Yohe,  Eds.,  2014.  Climate  Change  Impacts  in  the  United   States:  The  Third  National  Climate  Assessment.  U.S.  Global  Change  Research  Program:  841.  doi:10.7930/ J0Z31WJ2.  http://nca2014.globalchange.gov/   5 Turner,  B.  L.,  R.E.  Kasperson,  P.A.  Matson,  J.J.  McCarthy,  et  al..  2003.  A  framework  for  vulnerability  analysis  in   sustainability  science.  Proceedings  of  the  National  Academy  of  Sciences  of  the  United  States  of  America  100   (14):  8074–9.  doi:10.1073/pnas.1231335100 7 Adger,  Neil,  N.W.  Arnell,    and  E.L.  Tompkins.  2005.  Successful  adaptation  to  climate  change  across  scales.   Global  Environmental  Change  15  (2):  77–86.  doi:10.1016/j.gloenvcha.2004.12.005 8 IPCC.  2012.  Managing  the  Risks  of  Extreme  Events  and  Disasters  to  Advance  Climate  Change  Adaptation.  A   Special  Report  of  Working  Groups  I  and  II  of  the  Intergovernmental  Panel  on  Climate  Change  [Field,  C.B.,  V.   Barros,  T.F.  Stocker,  D.  Qin,  et  al.  (eds.)].  Cambridge  University  Press,  Cambridge,  UK,  and  New  York,  NY,  USA,   582  pp. 9 10 Ibid.,  2012. 25 when they occur. Responses to reduce risk may include proactive and reactive strategies, such as reducing exposure and vulnerability prior to events or changes, or increasing capacity to respond to and recover from events when they do occur. Conceptualizing  climate  risk   Evaluating and preparing appropriate responses to climate-related risk at community levels involves looking at a complex set of physical, societal, and ecological conditions and future trends at both global and local scales — in the context of: place, the built environment, and social constructs such as households, neighborhoods, and municipalities. To do this well involves ongoing collaboration between decision-makers, planners, stakeholders, and Figure 1.1 Assessing local climate-related risk Emissions & Socioeconomic Scenarios! Global Conditions! Climate! ! Natural Variability • Climate Change! Local Risk Conditions! s xpo ure ! E Weather &! Climate ! Events! ! Climate-related risk is more than the likelihood of occurrence of potentially hazardous events: risk is a confluence of factors (e.g. fire), exposure to that event, and vulnerability due to that exposure.! Risk! n Vul era y! bilit Adapted from IPCC SREX 2012! Local Resiliency Capacity! Coping! Global conditions, including natural variability and humandriven climate change, drive local weather and climaterelated events and trends! Adaptation! Response! Adapted from Turner et al 2003! !Local resiliency capacity helps reduce risk and involves coping and response capacity as well as the ability to adjust in ways that reduce vulnerability and exposure to conditions in the future.! Figure 1.1 describes the relationship between global conditions and local risk and resiliency. Projections of future climate rely upon scenarios of future greenhouse gas emissions and their effect on the climate from global to local scales. The risk to society depends on local exposure and vulnerability to those conditions. Local resiliency capacity which includes coping, response, and adaptation can help manage and even reduce that risk. 26 researchers.11 Figure 1.1 provides a conceptual model for how global climate conditions relate to local risk conditions and how local resiliency can support risk management and reduction. Making sense of climate-related risk (see Figure 1.1) • • • Global conditions, including natural variability and human-caused climate change, largely drive the weather and climate-related events and trends that occur locally. Climate-related risk is a confluence of hazard type (e.g. fire, drought), exposure to such an event or trend, and vulnerability to that exposure. Local resiliency capacity involves existing coping and response capacity as well as the ability to proactively adapt in ways that reduce vulnerability and exposure to conditions in the future as well as enhance response mechanisms for different temporal and spatial scales. Whereas local mitigation actions, such as reducing greenhouse gas emissions, can only minimally abate the future trajectory of global climate change, adopting and implementing adaptation strategies has a large potential to increase local resiliency and, as a result, reduce risk. Mitigation at the community level, however, is still critical in placing community actions in line with the Aspen Climate Action Plan and can have an outsized effect in demonstrating mitigation pathways that resonate with other communities and national audiences. Of course, the more communities around the world that take mitigation seriously, the lesser the impact of climate change. Moser, Susanne and Maxwell Boykoff, ed. 2013. Successful Adaptation to Climate Change: Linking Science and Policy in a Rapidly Changing World. 1st ed. New York: Routledge. 11 27 Credit: Aspen Historical Society CHAPTER  2:  HISTORICAL  OBSERVATIONS   Global  &  regional  trends   Temperatures in Aspen—as well as the region of the Southern Rockies—are on the rise. These trends mirror pronounced global rises in temperature that continue to be reaffirmed and updated by ongoing research. Most notably, in 2013, the International Panel on Climate Change (IPCC) Fifth Assessment Report examined updated evidence from climate observations and concluded: Warming of the climate system is unequivocal, and…many of the observed changes are unprecedented over decades to millennia. IPCC Working Group I Summary for Policy Makers, 2013 Global temperatures have risen sharply, particularly since the 1970s. Multiple lines of evidence have enabled scientists to attribute these changes, with high confidence, to use of fossil fuels and other human activities that produce greenhouse gases or alter land use. The trend over the past 130 years, between 1880 and 2012, depicts average surface temperature across the Earth as rising 1.5°F (0.8ºC). An increase of 1.3°F (0.7ºC) is observed from 1950-2012 (see Figure 2.1).12 U.S. national temperatures and regional temperatures in the Southwest, including Colorado, are also increasing, currently at a rate that surpasses the global rate of change. National temperatures rose approximately 2.0°F (1.1ºC) between 1978 and 2008. The state of Colorado  IPCC,  2013.  Summary  for  Policymakers.  In:  Climate  Change  2013:  The  Physical  Science  Basis.  Contribution   of  Working  Group  I  to  the  Fifth  Assessment  Report  of  the  Intergovernmental  Panel  on  Climate  Change   [Stocker,  T.F.,  D.  Qin,  G.-­‐K.  Plattner,  M.  Tignor,  S.K.  Allen,  J.  Boschung,  A.  Nauels,  Y.  Xia,  V.  Bex  and  P.M.  Midgley   (eds.)].  Cambridge  University  Press,  Cambridge,  United  Kingdom  and  New  York,  NY,  USA. 12 28 has shown a similar pattern, where average temperatures across the state of Colorado have increased by approximately 2°F (1.1ºC ) from the 1980’s to present and by 2.5ºF (1.4ºC) since the 1950s.13 Nationally, changes in precipitation as a response to global warming vary by region, with some areas seeing a decrease and other areas seeing an increase.14 Many regions have experienced levels of annual precipitation similar to their historical averages but have experienced an alteration in the timing or intensity of events.15 Figure 2.1 Observational record of annual mean temperature: Global, U.S., and Colorado Figure 2.1 shows the observational record from 1895-2012 of annual mean temperature at three different scales: for the globe, the U.S., and Colorado. The lines of the graph are smoothed over a 10-year running average and the temperature baseline from which departure is shown (represented by the gray dotted line) represents the 1971-2000 average. Source: Colorado Water Conservation Board (Lukas et al. 2014). 13  Lukas,  J.,  J.  Barsugli,  N.  Doesken,  I.  Rangwala,  and  K.  Wolter.  2014. Climate  Change  in  Colorado:  A  Synthesis   to  Support  Water  Resources  Management  and  Adaptation.  A  Report  for  the  Colorado  Water  Conservation   Board.  Western  Water  Assessment. 14  Melillo,  Jerry  M.,  Terese  (T.C.)  Richmond,  and  Gary  W.  Yohe,  Eds.,  2014:  Climate  Change  Impacts  in  the   United  States:  The  Third  National  Climate  Assessment.  U.S.  Global  Change  Research  Program:  841.  doi: 10.7930/J0Z31WJ2.   15Gao,  Y.,  L.  R.  Leung,  J.  Lu,  Y.  Liu,  M.  Huang  and  Y.  Qian.  2014.  Robust  spring  drying  in  the  southwestern  U.S.   and  seasonal  migration  of  wet/dry  patterns  in  a  warmer  climate.  Geophysical  Research  Letters  2014   GL059562. 29 2.2 Colorado annual precipitation, 1900-2012 Figure 2.2 shows precipitation across the state of Colorado at 9 monitoring locations since 1900. The thin, dotted lines for each data set shows the average precipitation for 1971-2000. For each station no significant trend is identified for precipitation at 30-, 50-, or 100-year timescales. Source: Colorado Water Conservation Board; Lukas et al. 2014. 30 Colorado’s statewide precipitation record from the NOAA database shows inter-annual variability but no noticeable trend of increase or decrease over the last century (Figure 2.2). The 2014 report Climate Change in Colorado, prepared by the Western Water Assessment, found no significant trend in annual precipitation across nine representative stations statewide since the 1900s, nor has there been a trend in droughts over this same time period. Historical proxies for water availability such as tree rings reveal that previous to the start of the 20th century, there were occurrences of droughts in Colorado of longer duration and greater severity than those seen in the past 100 years, indicating such mega-droughts could occur again in Colorado’s future.16 Colorado temperatures show a clearly discernible rising trend over the last century (Figure 2.1), and even if overall quantity of precipitation remains about the same in Colorado, warming temperatures can impact the water cycle. This pattern is pertinent to local ecological and hydrological conditions; water availability may decrease even if annual precipitation remains steady or increases slightly. Research indicates that increased temperatures may impact watersheds by causing increased evaporation, a shift toward a greater proportion of precipitation coming as rain rather than snow, earlier runoff, increased evapotranspiration, and drying of soil during the growing season—all of which have the capacity to diminish ecological water storage and availability.17 Water availability is likely to be a matter of future concern even under projections where annual precipitation is expected to remain relatively flat. Studies of snowpack across the Southwest have indeed noted a shift from snowpack-dominated toward rainfall-dominated water regimes.18 While the Roaring Fork watershed is likely to remain snowpack-dominated in the future, studies of snowpack in mountain areas suggest that increased temperatures combined with the phenomenon of dust-on-snow events, which decrease albedo and hasten melting, may both contribute to overall decreases in snow cover and accelerated melting rates. Colorado’s alterations in snowpack are comparable to trends elsewhere in the Southwest, with one study of the period 1979- 2007 revealing a shift of, on average, 2-3 weeks earlier peak streamflow timing and snowmelt events during the spring.19 16  Lukas  et  al.  2014.  Gao  et  al.  2014. 18  Barnett,  Tim  P.,  David  W.  Pierce,  Hugo  G.  Hidalgo,    Celine  BonIils,  et  al.  2008.  Human  Induced  Changed  in  the   17 Hydrology  of  the  Western  United  States.  Science,  319  (5866):  1080-­‐1083.  doi:10.1126/science.1152538  Clow,  David  W..  2010.  Changes  in  the  Timing  of  Snowmelt  and  StreamIlow  in  Colorado:  A  Response  to   Recent  Warming.  J.  Climate  23:  2293–2306.  doi:  10.1175/2009JCLI2951.1 19 31 Finally, consideration of climatic and hydrological trends should be considered in conjunction with societal trends in water demand. The Colorado River Basin services 40 million users and spans 7 states and 2 countries. Overall demand for water in the Basin has grown over the last century, and following the 2002 drought, demand for water resources exceeded supply for the first time. Use of the Colorado River is governed by a complex set of legal structures (i.e. the Law of the River). Further information on water supply and demand can be found through an extensive study published by The Bureau of Reclamation in 2012, which provides in-depth analysis of historical trends and future projections.20 Local  observa`ons   Table 2.1 Summary of Aspen area observations Observation Trend: 1940-1979 Trend since 1980 Average, Maximum, and Minimum Temperatures Average: 1.0ºF (0.6ºC) increase Average: 1.4ºF (0.8ºC) increase Min: 1.9ºF (0.1ºC) increase Min: 1.2ºF (0.7ºC) increase Max: 1.2ºF (0.7ºC) decrease Max: 1.7ºF (1.0ºC) increase Frost Free Days 11 day increase 23 day increase Annual Snow 1.6 inch increase 9.9 inch decrease Annual Precipitation 2.6 inch increase 0.6 inch decrease April 1st Snow Water Equivalent* Data not available 1.2 inch decrease Table 2.1 shows changes over time calculated from the trend line slopes for the duration of each station ’s record: from 1940-1979 and from 1980-2013 (Station 372). The 1940-1979 data was gathered from NOAA Station Aspen 370, while the 1980-2013 data is from the Aspen Station’s new location at 372, which is ~200 feet higher in elevation. *The data for April 1st Snow Water Equivalent is from the NRCS station located on Independence Pass and does not have data prior to 1980. Concurrent with national and global trends, average temperatures in Aspen continue to rise, following the same warming direction identified in the 2006 Aspen report. It should be noted that 20  U.S.  Bureau  of  Reclamation.  2012.  Colorado  River  Basin  Water  Supply  and  Demand  Study.  December  2012.   http://www.usbr.gov/lc/region/programs/crbstudy/Iinalreport/Study%20Report/ CRBS_Study_Report_FINAL.pdf 32 the Aspen record is based on the data of a single weather station. The data are collected by the National Weather Service and are accessible online through the National Climatic Data Center. Single station data tend to show greater variability from year to year than averages of data from multiple stations within a region. Temperature   Average temperatures in Aspen have risen by 1.4°F (0.8ºC) since 1980 compared with an increase of 0.8ºF (0.4ºC) during a base period of 1940-1969 (Figure 2.3). Using averages during the time 1940-1969 as a base period, the last decade (2004-2013) is 1°F (0.6ºC) warmer than the base period average. Importantly, the location of Aspen’s weather station changed in 1980 Figure 2.3 Average annual temperature in Aspen by decade Figure 2.3. The blue bars are decadal averages starting with the 1940s. The orange line is yearly averages. Average annual temperatures in Aspen have increased since 1940. Aspen Station 370 was moved from an in-town location to the Water Treatment Plant and re-designated Station 372 in 1980. The new station, approximately 200 feet higher in elevation, is anecdotally understood to be slightly cooler, but overlapping monitoring records are unavailable to verify this. Data source: NOAA-NCDC Aspen Stations 370 and 372. to a new location about 200 feet higher and 0.5 miles away from the initial site.21 Minimum and maximum temperatures observed using data from the Aspen station have behaved differently during the periods considered. Average minimum temperatures have increased across both periods: by 2.7°F (1.5ºC) from 1940-1969 and 1.2°F (0.7ºC) from 1980-2013. Average maximum temperatures, by contrast, decreased by 1.0°F (0.6ºC) between 1940-1969 but rose by 1.7°F (0.9ºC) from 1980-2013. This type of trend, where average  Since  the  record  is  not  continuous,  the  record  prior  to  1980  compared  to  after  the  station  move  is   somewhat  compromised. 21 33 minimum temperatures increase more than maximum temperatures has also been observed at larger spatial scales.22 Figure 2.4 Observed changes in minimum temperature by season Figure 2.4 shows average minimum temperature by season for each decade since 1940. The winter season is counted as beginning in December of the first year and carrying through continuously to January and February of the following year. The location of Aspen’s weather monitoring station changed in 1980, shifting upward in elevation ~200 feet. Data source: NOAA-NCDC Aspen Stations 370 and 372. The observed trend of increasing minimum temperatures has occurred across all seasons. Understanding seasonality in warming is important because dates of freezing temperatures impact the growing season, bud success, and water availability. Increases in minimums also affect the ability to make snow in November and December. Increases in spring minimum temperatures are of particular importance due to their effect on the timing and pace of snowmelt (Figure 2.4). Increasing minimum temperatures in winter also have impact on snow depth and duration, as they may lead to cold-season precipitation coming as rain rather than snow. In a  Braganza,  K.,  D.  J.  Karoly  and  J.  M.  Arblaster.  2004.  Diurnal  temperature  range  as  an  index  of  global  climate   change  during  the  twentieth  century.  Geophysical  Research  Letters  31(13):  L13217. 22 34 Figure 2.5 Observed changes in maximum temperature by season Figure 2.5 shows average maximum temperature by season for each decade since 1940. The winter season is counted as beginning in December of the first year and carrying through continuously to January and February of the following year. The location of Aspen’s weather monitoring station changed in 1980, shifting upward in elevation ~200 feet. Data source: NOAA-NCDC Aspen Stations 370 and 372. snowpack-dominated watershed such as Aspen’s a shift from snow to rain during winter will reduced water availability in the following warmer seasons. Generally, maximum seasonal temperatures at the Aspen station showed a less clear pattern since the 1940s than minimum temperatures, with the exception of the spring season. From 1980-2009 maximum temperatures for the spring months show a rise each decade (Figure 2.5). Observation of warming since the 1940s is especially evident in number of frost free days per year.The last ten years, 2004-2013, showed an average of 30 more frost free days per year than the annual average of the 1940-1969 base period (see Figure 2.6) and an average of 23 more frost free days per year just since 1980 (see Table 2.2). A longer frost free period may offer opportunities in terms of crop production, but it will also alter natural cycles, such as timing relationships between animals and their food sources. Additionally, over time distinct habitats of the valley may change in appearance as vegetation shifts in response to climate conditions. 35 Figure 2.6 Frost free days in Aspen Figure 2.6 shows a rise in average consecutive frost-free days since the 1940’s. The blue bars show decadal averages, and the orange line shows yearly frost free days. The location of Aspen’s weather monitoring station changed between 1979 and 1980, shifting upward in elevation ~200 feet. Data source: NOAA-NCDC Aspen Stations 370 and 372. Precipitation Precipitation records in Aspen show high year-to-year variability, and the data set from the original Aspen station (Station 370, 1940-1969) differs in slope direction from the current data set (Station 372, 1981-present). From 1940-1969, average yearly precipitation increased by 2.9 inches. Since 1980, measurements at the new station have shown an 0.6 inch decrease in total yearly precipitation. The wide range of variation possible between years can be seen in the high precipitation of 1984 and the low precipitation of drought years such as 2002 and 2012. Annual average precipitation from 2004-2013 was 24.5 inches. Comparatively, the base period annual average rainfall from 1940-1969 was 18.8 inches. Again, the upward shift in precipitation after 1980 may be the result of the station change, but this is a speculation that cannot be confirmed. Unfortunately, the National Climatic Data Center (NCDC) does not provide overlapping data, and no statistical conclusions about the time period of the switch can be inferred (see Figure 2.7). Similar to precipitation, total snowfall for a winter season showed a 9.6 inch increase over the period from 1940-1969, but over the time period of 1981-2013 there is a 9.9 inch decrease in winter-season snowfall (Figure 2.7). When the overall averages of two time periods are compared, however, 1981-2013 has, so far, been wetter than the average of the previous 30 years. Average winter-year snowfall from 1940 to 1969 was 134.8 inches. After the station 36 change, from 1981-2013, the average rose to 170.2 inches (Figure 2.8,Table 2.1). The increase is in part driven by the fact that snowfall in the winter of 1983/1984 marked a new record high in Aspen’s data set with 279 inches of snowfall in a single winter season. This contrasts with the winter of 1976/1977, which was the lowest snowfall since 1940 with only 61 inches. (This analysis of 1940-2013 precipitation and snowfall omits data from years with two or more months missing data). At 173.9 inches, average snowfall in Aspen in the last ten years (winter of 2004spring 2013) is similar to the overall average snowfall of 170.2 inches during the entire 1981-2013 period. Although data on precipitation patterns for Aspen do not illustrate notable directional trends, total annual precipitation or total winter-season snowfall are not the only factors critical in determining water availability in this region. Duration of snowpack, quantity of snow, dust on snow, and rain on snow events can all play an important role in water availability and timing throughout the summer. Figure 2.7 Annual precipitation in Aspen Figure 2.7 shows calendar-year annual precipitation in Aspen. Precipitation does not show a clear increase or decrease over time, although there is a shift in precipitation coincident with the station move in 1980. The location of Aspen’s weather monitoring station changed in 1980, shifting upward in elevation ~200 feet. Data source: NOAA-NCDC Aspen Stations 370 and 372. Streamflow   Trends in river flows, such as timing of peak runoff and discharge at peak, can also serve as indicators of changing precipitation and temperature patterns. However, the Roaring Fork Valley is a highly managed watershed with trans-basin and within basin diversions with flows determined by a variety of factors. Climate is just one of these factors, and all factors act in 37 Figure 2.8 Annual snowfall in Aspen Figure 2.8 shows total winter-season snowfall for Aspen, which does not show a clear increase or decrease. A single year of snow was calculated as the total from the first snowfall in the autumn (August or later) of one year through the last snowfall in spring the following year (July or earlier). The location of Aspen’s weather monitoring station changed in 1980, shifting upward in elevation ~200 feet. Data source: NOAA-NCDC Aspen Stations 370 and 372. concert. In this section, an analysis of annual peak flows on the Roaring Fork River is provided, and these variables are discussed again in greater detail in the Chapter 4 section on water. Data collected from the Glenwood Springs USGS station on the Roaring Fork River at the confluence with the Colorado River integrate many key upstream factors and can offer some insight into the timing and quantity of peak flow of the Roaring Fork River. Patterns at this station, however, are affected by natural variability, climate change, and water management. Additional factors include total precipitation, timing of precipitation, quantity of runoff from snowpack, upstream water use, water storage, in-basin diversions, and trans-mountain diversions to the Front Range (Figure 2.9).23 Additionally, a new area of research suggests the importance of the effect of dust on snow events in mountain hydrology. When dust settles onto snow, it decreases the snow’s albedo, or reflectivity, meaning that that snow absorbs more of the sun’s radiation, causing it to warm, and thus melt faster. A recent study about dust impacts on mountain snowpack in the Colorado River Basin found that existing perturbations from dust loading in the Colorado Rockies may be advancing peak runoff in the Colorado River by three weeks as measured by streamflow at  A  more  complete  analysis  of  gage  data  and  simulated  data  at  different  nodes  in  the  Roaring  Fork  system  or   diversion  and  use  impact  on  speciIic  reaches  of  the  Roaring  Fork  watershed  are  available  in  the  State  of  the   Roaring  Fork  Watershed  Report  2008:  http://www.roaringfork.org/sitepages/pid272.php. 23 38 Lee’s Ferry, with the potential for an additional three week earlier onset during extreme dust events.24 While multiple natural variables contribute to determining peak flow, these variables also occur within the context of water management for human needs. The Roaring Fork River both serves as a source of municipal and agricultural water for local residents and is heavily diverted to the Front Range to meet trans-basin diversion agreements. Although little can be determined about climate-related shifts in river volume from USGS streamflow and peak discharge numbers alone, trends in streamflow describe the context in which the resiliency planning process occurs. Annual peak flow measurements for the GWS station show a decline in peak flow since the 1940s. Diversions are an important factor during the time period shown (Figure 2.9) 
 Figure 2.9 Annual Roaring Fork River peak flow at Glenwood Springs Figure 2.9 shows the date of peak discharge in CFS at the Glenwood Springs gage station since 1940. Peak for individual years and peak timing are impacted by a variety of factors such as precipitation, diversions, storage, evaporative losses, ground water recharge, and dust on snow. Source: USGS GWS Gauge Station. 24 Deems, J. S., T.H. Painter, J.J. Barsugli, J. Belnap, and B Udall. 2013. Combined impacts of current and future dust deposition and regional warming on Colorado River Basin snow dynamics and hydrology. Hydrology and Earth System Sciences 17 (11): 4401–4413. doi:10.5194/hess-17-4401-2013 39 Resources  for  access  to  observa`onal  data   Ongoing monitoring of recent Table 2.2 Comparison of recent decade to conditions in comparison to prior 1940-1969 average normal conditions can be one benchmark for assessing how much Observation Base Period Last Decade Average Average local conditions have or have not (1940-1969) (2004-2013) departed from normal conditions. For example, Table 2.2 provides a comparison of the most recent ten Ave: 41ºF (5.0ºC) Ave: 42ºF (5.6ºC) Average, years, 2004-2013, to historical Minimum, and Min: 25ºF (-3.9ºC) Min: 28ºF (-2.2ºC) conditions during a 30-year base Maximum Temperatures period, 1940-1969. Further Max: 56ºF (13.3ºC) Max: 56ºF (13.3ºC) information on past and current conditions can be found online through the US Geological Survey, Frost Free Days 79 days 109 days the National Climatic Data Center (NOAA), and the National Resource Total Annual 18.8 inches 24.5 inches Precipitation Conservation Service (operators of Table 2.2  shows averages from a base period time, SNOTEL monitoring network). 1940-1969, in comparison with averages from the last decade, Local information on river health 2004-2013. The 1940-1969 data was gathered from NOAA can be obtained through the Station Aspen 370, while the 1980-2013 data is from the Aspen Station’s new location at 372, which is ~200 feet higher in Roaring Fork Conservancy. In the elevation. near future the Integrated Roaring Fork Observation Network (iRON), a site to be developed by AGCI, will offer Valley-specific information about ecological parameters and collected data for climate parameters. As discussed in Chapter 6, ongoing monitoring and analysis of environmental conditions, as well as monitoring of societal and ecological indicators, is a crucial component in creating strategies for successful adaptation to the local changes in climate. 40 CHAPTER  3:  CLIMATE  MODELING  RESULTS     Introduc`on   Box 3.1 Key points from modeling results Climate modeling for the region surrounding Aspen reinforces the finding from the 2006 Study that temperatures will increase. As in 2006, the magnitude of future warming is dependent on global greenhouse gas emissions, with higher emission scenarios producing greater projected changes within the models. In terms of precipitation, new modeling analysis prepared for this study indicates slight increases in projections of future annual precipitation, with important seasonal variation. Higher emissions scenarios tend to equate to larger shifts in precipitation. Changes in storm tracks, global scale patterns such as the jet stream, loss of Arctic sea-ice, and heat uptake and release by the oceans are all active areas of research. As the climate warms in response to the build-up of greenhouse gases, patterns of the past may no longer • Climate projections for the Aspen region significantly depend on future global greenhouse gas emissions. Rise in global average temperature among low (RCP4.5) emissions is projected to be 5.3ºF (3.0ºC), versus 9.7ºF (5.4ºC) for high (RCP8.5) emissions, by 2100. • Modeling for the Aspen region projects increasing temperatures among all emissions scenarios over 21 Median results for the end of the century under a high emissions scenario suggest a nearly 10ºF rise in temperature by 2100. • Precipitation projections for the Aspen region remain more uncertain relative to temperature but overall indicate a slight increase. In many models, Colorado lies in a zone wherein projected drying in the Southwest transitions to projected wetter conditions in higher latitudes. As a result, models considering the Aspen region project a range that include increases and decreases in precipitation as well as little to no change. 41 Figure 3.1 Scenarios of global carbon emissions and temperature change provide an appropriate guide for projecting the future.25 As a result, dynamic models of the Earth’s climate become the primary tool available to characterize possible future climate conditions at global and regional scales. Figure 3.1 Four different scenarios of global CO2 emissions (in trillion grams of carbon per year) for the 21st century. Based on the emissions scenarios utilized in the IPCC 5th Assessment Report (AR5), each scenario is labeled with an estimated global average temperature increase above pre-industrial levels, as produced by an ensemble of climate models. Observed emissions (black circles) continue to track the highest scenario (RCP8.5). Note that the lowest emission scenario (RCP2.6) requires negative emissions and that the projections in all scenarios do not include the effect of deforestation. Figure source: Sanford et al. 2014. A key set of inputs into modeling future climate is greenhouse gas emissions, which are based upon global energy and land use assumptions. The climate modeling community has adopted a new set of emissions scenarios known as Representative Concentration Pathways (RCPs), which are used in this report as well as the Fifth Assessment Report of the IPCC. These new scenarios are referred to as RCP2.6 (low), RCP4.5 (medium), RCP6.0 (medium-high), and RCP8.5 (high). The lowest scenario, RCP2.6, requires negative emissions by the later part of the century and is not considered in the analysis for this study.26,27 Generally speaking, climate models represent climate processes more accurately over larger spatial and longer temporal scales. Higher confidence is placed on projections of  Vano,  Julie  A.,  Bradley  Udall,  Daniel  R.  Cayan,  Jonathan  T.  Overpeck,  et  al..  2014.    Understanding   Uncertainties  in  Future  Colorado  River  StreamIlow.  Bulletin  of  the  American  Meteorological  Society  95  (1)   (January):  59–78.  doi:10.1175/BAMS-­‐D-­‐12-­‐00228.1.  http://journals.ametsoc.org/doi/abs/10.1175/BAMS-­‐ D-­‐12-­‐00228.1. 25  Modeling  results  in  Chapter  3  primarily  draw  from  a  set  of  emissions  scenarios  called  Representative   Concentration  Pathways  (RCPs).  The  lowest  RCP  (2.6)  indicates  near  term  leveling  off  and  reduction  of   greenhouse  gas  emissions  over  time.  Other  RCPs,  in  rising  numerical  order,  present  higher  and  higher   assumptions  of  future  emissions,  with  the  highest  (8.5)  representing  the  current  trend  of  the  global  economy.   27 IPCC  2013 26 42 temperature than projections of precipitation. Near term, or decadal climate projections (i.e. 10-20 years) are in development and are not utilized in this study.28 In the Southern Rockies, even the high resolution models cannot fully resolve the effects of mountain topography on regional climate systems. Whereas the majority of results presented in 2006 were produced using modeling assessed in the Intergovernmental Panel on Climate Change (IPCC) Third Assessment Report (2001), the results presented here stem from work assessed in the Fourth and Fifth Assessment reports (2007 and 2013-14, respectively).29 In this section, we update 2006 findings by utilizing subsequent generations of models not fully available in 2006 including: • • • Emissions scenarios and global temperature projections Temperature and precipitation modeling results for the western Colorado region Surveys of other regional projections of temperature and precipitation Emissions still matter As in previous modeling analysis, climate projections assessed since 2006 continue to identify future greenhouse gas emissions, with CO2 as the largest contributor, as the single most determinant factor in the amount of future increases in global average temperature change.30 Moreover, since 2006, actual global emissions continue to follow the high emissions scenario. As Figure 3.1 illustrates, the range of global average temperature increase between the highest and lowest emission scenarios in 2100 is more than 6ºF (3.4ºC). From this analysis, three points are relevant to Aspen: • • • 28 Efforts to mitigate future emissions of greenhouse gases can dramatically affect the overall magnitude of climate change experienced during the 21st century. The world is still on a high emissions trajectory with current and future alteration of climatic conditions that will have local repercussions. Multiple future pathways of climate change are possible and, as a result, planning for climate change should consider how to adjust to a range of potential outcomes.  See  chapter  11  in  IPCC  2013. 29  IPCC  2001,  2007,  2013  [full  citation  provided  in  references]   30  Moss,  Richard  H,  Jae  A.  Edmonds,  Kathy  A.  Hibbard,  Martin  R.  Manning,  et  al..  2010.  The  Next  Generation  of   Scenarios  for  Climate  Change  Research  and  Assessment.  Nature  463  (7282)  (February  11):  747–56.  doi: 10.1038/nature08823;  Sanford,  T.,  Frumhoff,  P.  C.,  Luers,  A.,  &  Gulledge,  J.  2014.  The  climate  policy  narrative   for  a  dangerously  warming  world.  Nature Climate Change,  4 (3),  164–166.  doi:10.1038/nclimate2148;  IPCC,   2013. 43 As an update in this report, we present modeling analysis results from the most recent generation of GCM outputs for the western Colorado region. Utilizing the identical technique and study area implemented in an earlier generation of GCMs available in 2006 (CMIP3), these projections are based on the more recent CMIP5 and are intended to provide an updated glimpse of future temperature and precipitation possibilities for the Aspen region (see Appendix B, Figure B.1 for map of the region considered in this modeling analysis).31,32 A description of the methods utilized to derive these projections as well as additional data output from these projections is available in Appendix B. Table 3.1 provides a summary of the projected changes further elaborated in the sections below. Table 3.1 Projected changes in temperature & precipitation for western Colorado Change from historical period 1980-1999 Temperature change in ºF (ºC) Precipitation change (%) Medium Emissions Scenario (RCP4.5) 2020-2039 +2.8 (1.6) +1.4 2050-2069 +4.5 (2.5) +2.4 2080-2099 +5.3 (3.0) +3.1 2020-2039 +2.3 (1.3) +0.6 2050-2069 +4.3 (2.4) +1.7 2080-2099 +6.6 (3.7) +5.4 2020-2039 +2.9 (1.6) +1.9 2050-2069 +6.2 (3.5) +3.0 2080-2099 +9.7 (5.4) +4.2 Medium-High Emissions Scenario (RCP6.0) High Emissions Scenario (RCP8.5) Table 3.1. displays annual average changes in temperature and precipitation projected for three time periods and three emissions scenarios using an ensemble of Climate Model Diagnosis and Intercomparison Project (CMIP5) model output. Changes projected are relative to the historical period— 1980-1999. There is more confidence in temperature projections than precipitation projections. Data source: Model output analysis provided by C. Tebaldi, NCAR  CMIP  refers  to  the  Coupled  Model  Intercomparison  Project,  an  international  effort  that  coordinates  climate   and  Earth  system  modeling.  For  more  info  see:  http://cmip-­‐pcmdi.llnl.gov/   31 32  A  description  of  the  results  and  methods  utilized  in  2006  are  provided  in  section  2.5.4  (p  28-­‐29)  as  well  as   in  Appendix  C  (p.113-­‐119)  in  AGCI,  2006. 44 Projected  changes  in  temperature  &  precipita`on  for  western  Colorado   Results from this modeling work include projected mean temperature and precipitation as well as seasonal projections of temperature and precipitation presented as probability distributions. Results are presented for projection periods 2020-2039, 2050-2069, and 2080-2099 and represent values for an average year during each period. Full seasonal analysis as well as a comparison between the 2006 Study and the 2014 Study results is provided in Appendix B. A summary of projections is provided in Table 3.1. Temperature  results   Temperatures in the Aspen region are projected to increase among all scenarios considered and in all seasons. By 2030, there is no significant difference in the projection of temperature between scenarios, but by 2090 there is nearly a 4.5ºF (2.5ºC) change between median projections under the high (RCP8.5) and medium (RCP4.5) emissions scenarios. Under high emissions scenarios by the end of the century, temperatures are projected to increase more during summer and fall months than during winter and spring months. See Appendix B for more detail. Precipita`on  results   There is much more confidence in regional projections for temperature than for precipitation, and precipitation is likely to remain uncertain due to challenges of climate projections in mountainous regions. Median projections of precipitation considered in most seasons under most scenarios indicate a slight increase in precipitation by 2030 and by 2090. However, a small percentage of model results project either significantly less or significantly more than historical amounts of precipitation. These results underline a significant point for resource management in the context of climate change: that uncertainty in projections calls for new planning methods that account for multiple possible future scenarios.33 This approach is consistent with past planning approaches where both positive and negative extremes from natural variability (i.e. drought years and flood years) are incorporated in management strategies, but recognizes that climate state of the 20th century is in transition and no longer a reliable guide. See Appendix B for more detail. Regional  precipita`on  projec`ons   Projections for precipitation change in the Southern Rockies, particularly in Colorado, are fraught with uncertainty, due in part to the challenge of resolving intricate micro-scale climate processes in the Rocky Mountains using the coarse resolution of global-scale climate models. Colorado has been identified to be on a “transition zone,” situated between a section of the Means,  E.  I.,  &  Kaatz,  L.  2010.  Decision  Support  Planning  Methods:  Incorporating  Climate  Change   Uncertainties  into  Water  Planning.  Water  Utility  Climate  Alliance. 33 45 Figure 3.2 Observed and projected precipitation in Colorado Figure 3.2 shows observed and projected annual precipitation changes in Colorado. Blue/orange bars represent observations 1950-2012. The dotted purple line represents the median of 37 model projections (individual model results shown in blue). The black dot represents the median result for the projection period 2035-2064 with the solid purple line representing the range of results from the 90th to the 10th percentile. All results are relative to 1971-2000 base period. Source: Colorado Water Conservation Board; Lukas et al. 2014. North American continent that is anticipated to become wetter to the north and a section that is anticipated to become drier to the south throughout the course of the 21st century. Nevertheless, the central tendency of precipitation projections for the state show only slight change by the middle of the century under a medium emissions scenario, RCP4.5 (see Figure 3.2). Model results therefore do not significantly agree upon precipitation projections for Colorado as a state and less so for specific regions of Colorado.34 One of the steps in validating a new generation of models is adjusting for possible bias from observed conditions. This is an area of active research, but early indications suggest that CMIP5 modeling contains a wet bias in precipitation projections for our region, meaning that actual future conditions may actually be drier than current models suggest under any given scenario.35 In addition, in many regions, models do not agree on whether a human-induced climate signal can be distinguished from 34  Lukas  et  al.  2014 35  Ibid.   46 47 Figure 3.3 shows temperature projections from studies and assessments during the period 2006-2014 that were conducted for areas including or near by the Aspen area. Due to differences in geographic scope and methodology, the results provided here are intended for impressionistic comparison. Indicator colors of blue, orange, and red indicate various low, medium, and high emissions scenarios. The historical base period for Aspen MAGICC/SCENGEN results is 1976-2005; for Aspen PCMDI is 1980-1999; for Christensen & Lettenmaier (2006) is 1950-1999; for Ray, Barsugli, & Averyt is 1950-1999; for USGCRP 2009 is 1960-1979; for Stratus (2012) is 1950-1999. Projection ranges, as cited by the studies, are indicated by whisker plots. Black whiskers represent .25 and .75 range of model results with icon centered on .50 percentile; grey whiskers indicate .10 and .90 range of model results with icon centered on .50 percentile; purple whiskers represent high-end and low-end results among several scenarios with indicator centered on arithmetic mean Figure 3.3 Temperature projection comparisons for Colorado and Southwest region 48 Figure 3.4. shows precipitation projections from studies and assessments during the period 2006-2014 that were conducted for areas including or near by the Aspen area. Due to differences in geographic scope and methodology, the results provided here are intended for impressionistic comparison. Indicator colors of blue, orange, and red indicate various low, medium, and high emissions scenarios. The historical base period for Aspen MAGICC/SCENGEN results is 1976-2005; for Aspen PCMDI is 1980-1999; for Christensen & Lettenmaier (2006) is 1950-1999; and for Stratus (2012) is 1950-1999. Cited projection ranges are indicated by whisker plots. Black whiskers represent .25 and .75 range of model results with icon centered on .50 percentile; grey whiskers indicate .10 and .90 range of model results with icon centered on .50 percentile. Results for 2020, 2050, 2090, and 2100 are shown slightly separated for clarity. Figure 3.4 Precipitation projection comparisons for Colorado and Southwest region natural variability in precipitation, even by the end of the century.36 Regional  temperature  and  precipita`on  projec`on  comparisons   To present insights from modeling work conducted since 2006 for regions including or near to Aspen, a literature review was conducted that considered scientific publications and assessments containing temperature and precipitation projections. The projections contained within each of the publications examined were extracted along with relevant metadata such as study area, model selection process, emissions scenarios considered, base period, and uncertainty range. Results from this literature survey are plotted on Figures 3.3 and 3.4 along with selected results from the 2006 Study. Due to the diversity of methods utilized in different studies, these figures are intended to be impressionistic in order to highlight general areas of agreement or disagreement between recent results and those presented in the 2006 study. Figure 3.3 indicates that among all the results in the literature surveyed, including results from the 2006 Study, increases in temperature are projected among all emissions scenarios. Toward the end of the century, the temperature increase projections for Aspen’s region (2006) under middle emissions scenarios are comparable to the high emissions scenario results for Boulder, Colorado and the Colorado River Basin. This is consistent with expectations that higher elevation areas are anticipated to warm more relative to lower regions. Figure 3.4 indicates that among nearly all the results in the literature surveyed, the midpoint or 50th percentile result for precipitation change is projected as a slight decrease. However, the range of results for each projection includes the possibility for minor increases in total annual precipitation, and some projections under low and medium emissions scenarios forecast slight increases in precipitation. These projections are consistent with the results from the 2006 Study that indicated decreases in precipitation for midrange estimates but included ranges of uncertainty that incorporated even more significant decreases in precipitation as well as increases. These results, however, differ from new modeling presented in the previous section in that, for those updated results, median projections indicate a slight increase in precipitation. Tebaldi,  C.,  Arblaster,  J.  M.,  &  Knutti,  R.  2011.  Mapping  model  agreement  on  future  climate  projections.   Geophysical  Research  Letters,  38(23).  doi:10.1029/2011GL049863 36 49 CHAPTER  4:  SECTORAL  IMPACTS   Introduc`on   At scales from global to local, climate change is anticipated to bring about a wide range of impacts that affect many, if not all, of the sectors critical to the economic and environmental wellbeing of communities. In this report, we provide an overview of potential impacts to key sectors in the Aspen community: Recreation & Tourism Water Ecosystems Public Health & Safety Energy Built Environment & Infrastructure • • • • • • These sectors were chosen in consultation with the City while setting the scope of this study. The scope was not able to include every sector, although other sectors such as agriculture are likely to be impacted by climate change as well. Many of the climate-related trends and events affecting different sectors are similar, and the impacts on sectors are interrelated. As a Impacts within sectors important to Aspen consequence, effective resiliency planning often are interrelated. Effective planning will involves addressing impacts to multiple sectors at likely include an integrative approach, once. In Aspen’s situation, water is a critical considering resiliency in multiple sectors at resource to every sector examined in this report. once. As illustrated in Table 4.1, climate-related changes or events, ranging from incremental to transformational, will influence each of the sectors analyzed in this report in multiple ways. The more significant the increase in atmospheric carbon dioxide, the more significant the impacts that can be expected in a particular sector. As a result, societal response will likely occupy a spectrum from gradual, incremental adjustments to more substantial, transformational changes. Changes will likely involve technical, behavioral, and policy adjustments and will occur at individual as well as organizational (e.g., NGOs and private sector) and governmental levels. Discussion of response strategies—ideas for how to approach resiliency planning—are provided within each sectoral subchapter. While this overview highlights many of the impacts expected for sectors in the Aspen community, much of the research available is not specifically focused on Aspen. Therefore, limited statements can be made about expected changes particular to Aspen. The report focuses on generalized impacts from research focusing on the Southern Rockies and North America to draw conclusions relevant to Aspen’s resiliency planning. 50 51 Weather Climate Related Event or Trend Table 4.1 Summary of possible impacts by sector Ecology Water Recreation Examples of Possible Impacts Health Safety Energy Built Environment Incremental Change Transformative Change Change In average annual temperature Gradual uphill shifts in plant and animal species Evaporative losses from river and soils; changes in quality, quantity, timing of river flows Challenge meeting target ski area conditions; alterations to timing of rec. seasons Increased vulnerability to heat stress for vulnerable populations elderly); increase in potential for VBD Changes in energy demand and supply patterns over time Changes in HVAC requirements Increase In frost free days Increase in growing season; potential for invasive species Early drying of soil in summer; greater irrigation demand Expansion of summer recreation; impaired snowmaking conditions Lengthened, intensified allergy season; increased fire risk Increase in demand for energy for cooling systems; seasonal shifts in energy requirements Deployment of efficient irrigation systems; change in engineering standards Change to local hydrology Expansion of dry climate species; altered river ecology Temperature driven evaporative losses Shortened winter season; timing mismatch for rafting Increased fire danger; air pollution from fire Altered hydroelectric supply pattern High water and low water impacts to infrastructure Chengee In extreme tempo Extreme Precipitation Severe fire Heat/drought stress to sensitive species Increased evaporation, evapotranspiration Reduced conditions for snowmaking Increased potential for heat stress; lengthened, intensified allergy season Increased energy demand for cooling systems such as AC Greater deployment of intolerable conditions within existing systems Iconic species at risk Sudden Aspen Decline) Restrictions on water use; further risk of over- allocation ?76/?02 like skiing conditions; summertime wilderness use restrictions Regional impacts to agriculture, local food production Decreased water availability for hydroelectric production Less water available for municipal use Destruction of some habitats High water flows; localized flooding; Hazards to recreational users and infrastructure Flooding, flash flooding, landslides Interruptions to energy production and distribution systems Flood damage to buildings, bridges, roads Dramatic alteration to landscape Debris flows into river; water quality impacts Damage to recreational infrastructure; degraded aesthetic quality Personal endangerment; heightened air quality risk Impairment and/or destruction of energy production and distribution Destruction of infrastructure and structures RECREATION  &  TOURISM       Changes  to  Aspen’s  winter-­‐based  tourism
 In the 2006 Aspen Study, Snowmelt Runoff Model (SRM) and SNTHERM results projected deteriorating skiing conditions on Aspen Mountain over the course of the 21st century among high, medium, and low emissions scenarios. For the highest emissions scenario considered, an end In 2006, modeling assessed by AGCI to skiing in Aspen was projected by 2100. So far projected an end of skiing in Aspen by the world continues to follow this high emissions 2100 under high emissions scenario. pathway.37 
 World emissions still continue along this pathway. Historical observations and projected future changes in the Aspen area reinforce findings from 2006. These observed and projected changes pose significant challenges to winter recreation, based on the sensitivity of natural snow abundance and quality to changes in temperature and precipitation. A survey conducted by the National Resources Defense Council (NRDC) showed that snow conditions do influence statewide demand for skiing in Colorado. The NRDC study found an 8% variance in skier days between high and low snowfall years. Although this variance was less than in other states’ surveys, in Colorado 8% translates to 1.86 million fewer skier visits during a low snowfall year as compared to high snowfall year.38 37  Sanford  2014;  IPCC  2013. 38  Burakowski,  E.  and  M.  Magnusson.  2012.  Climate  Impacts  on  the  Winter  Tourism  Economy  in  the  United   States.  National  Resources  Defense  Council,  (December). 52 For decades, ski areas have adapted to natural variability by altering their opening and closing dates and by developing and expanding snowmaking capacity.39 Snowmaking in Aspen, in its existing form, enables resort managers to achieve target conditions in time for a Thanksgiving opening and to sustain conditions through a springtime closing date. In recent years the Aspen Skiing Company has moved to reduce operational constraints from energy and water associated with snowmaking.40 However, climate-related barriers to snowmaking remain beyond the control of ski resort managers. One fundamental challenge due to climate change is the likely reduction of cold temperatures required for adequate snow production.41 A still unexplored component of a shift to increased snowmaking is consumer reaction to increased dependence on snowmaking.42 Additionally, observations suggest that precipitation coming as rain instead of snow during the skiing season will be increasingly common, as was discussed in the 2006 Study. Knowles, Dettinger, and Cayan conducted a study on trends in the fraction of winter (Nov-Mar) with precipitation falling as rain versus snow in the Western United States for 1949-2004. Of the 261 sites analyzed, 74% showed the water content from snow In Colorado, 1.86 million fewer as a smaller fraction of total precipitation.43 In addition to skier visits occur during a low managed downhill terrain, these types of impacts may snowfall year as compared to high also affect the safety and desirability of other winter snowfall years. recreation activities like cross country skiing and back country skiing. As demonstrated in the 2006 Study using economic base analysis, winter recreation has been the magnet and economic engine for numerous related components of Aspen’s culture and economy—from restaurants, outfitters, and professional services to sizable real estate transactions, home remodels, and home building. Some of the visitors in the winter may not ski but come for other reasons associated with the ski culture. All of these things considered, changing future winter climatic conditions in Aspen and relative winter conditions in other resort communities may affect, positively or negatively, the overall allure for visitors to Aspen 39  Bark,  R.  H.,  B.G.,  Colby  and  F.  Dominguez.  2009.  Snow  days?  Snowmaking  adaptation  and  the  future  of  low   latitude,  high  elevation  skiing  in  Arizona,  USA.  Climatic  Change  102  (3-­‐4):  467–491.  doi:10.1007/ s10584-­‐009-­‐9708-­‐x 40  Interview  with  Rich  Burkley,  Aspen  Skiing  Company,  January  17,  2014 41  UN  World  Tourism  Organization,  &  UN  Environmental  Programme.  2008.  Climate  Change  and  Tourism:   Responding  to  Global  Challenges.  Madrid,  Spain.  Retrieved  from  http://sdt.unwto.org/sites/all/Iiles/docpdf/ climate2008.pdf 42  Bark  et  al.  2009 43  Knowles,  N.,  Dettinger,  M.,  &  Cayan,  D.  2006.  Trends  in  Snowfall  versus  Rainfall  in  the  Western  United   States.  Journal  of  Climate,  4545–4559.  Retrieved  from  http://journals.ametsoc.org/doi/abs/10.1175/ JCLI3850.1 53 Box 4.1 Recreation and tourism summary Climate-related changes: • Increasing wintertime temperatures • Reduced fraction of precipitation falling as snow • Increasing stream temperatures • Alterations to timing and quantity of stream runoff Future Potential Impacts • Difficulty meeting target ski area conditions during existing season • Reduction in suitable weather conditions for snowmaking • Alterations to timing of ideal summer and winter recreation conditions • Degraded aesthetic quality of environment; increasing hazards posed to visitors Potential Responses • Increased reliance on snowmaking • Marketing and communication to attract visitors at non-traditional times • Diversification of tourism in relation to economic base • Extension of summer season events and activities • Development of long term plans among providers of recreation and tourism services Opportunities • Expanded time period for summer season activities • Reduction of shoulder season lull Lingering Uncertainties • Future trends in overall snowfall • Adaptability and preferences of visitors • Cascading effects of climate change on Aspen’s economy throughout the entire year. It is not possible to predict in this study how specific conditions may play out for local economy and future investment, but potential scenarios could be considered with the help of additional research and engagement with stakeholders. As pointed out in the 2006 study, because of Aspen’s relatively high and cold ski mountain terrain relative to many other resorts, its skiing conditions may be superior to many other resorts as climate change progresses. Changes to Aspen’s summer-based tourism Climate-dependent recreational activities during the summer include water-based activities, such as rafting and fishing, and activities in the forest, such as hiking and biking. Changing conditions within the forest may result in indirect impacts to activities such as hiking and mountain biking. This section addresses the more direct and significant potential impact on recreation from alterations to the hydrograph. The 2006 Study presented runoff modeling results that projected substantial alteration in the timing of peak flows of the Roaring Fork River at Woody Creek. Subsequent to this, a statewide study by Clow analyzed data from 70 SNOTEL stations and dozens of gauge stations across the state. This research found that in the past 29 years there has been a 2-3 week timing shift in snowmelt and runoff. These types of changes, along with low flow years, may in the 54 future cause the timing of rafting demand to go out of sync with ideal rafting conditions on the upper Colorado River.44 Climate change could also significantly alter recreational fishing, a summer tourist attraction in the Aspen area. Warming stream temperatures have the potential to impact success of trout and other cold water sport fish by altering timing of growth and development and changing availability of food supplies.45 Along with impacts directly associated with warmer temperatures, aquatic habitat attributes such as dissolved oxygen and stream depth are affected by temperature and streamflow.46 Simple climate-related snowmelt modeling of the upper Roaring Fork indicates a likelihood of reduced snowpack with earlier peak runoff and greater seasonal flow variability during the 21st century.47 As recent observations (see Figure 2.6 on frost-free days) and future projections (see Chapter 3) suggest, the length of Aspen’s warm season is elongating. This presents an opportunity for expanded summertime recreational activities during what has typically been considered an “off season” or “shoulder season.” However, expanded summertime recreation will present new challenges for water and land resource managers, who will have to plan for new demand and potential impacts from increased resource use. Another component of climate-related change to summer tourism is the potential for wildfire risk to increase with drier conditions and higher temperatures. The risk of fire, as well as other extremes such as drought and flood, may affect both the logistical ability as well as the desire to engage in summertime activities before, during, and/or after these type of sudden events. In addition sudden changes such as fire and even more prolonged, gradual changes from drought can significantly affect the aesthetic character of the landscape, a notable attraction of the area for tourists.48 Response strategies The response strategies undertaken by providers and users of recreational services will vary according to existing capacity to adapt, the magnitude of change anticipated or experienced, and the overall sensitivity to actual or projected changes. For instance, ski area operators are experienced with and have many existing options at their disposal to respond to climate and Clow,  D.  W.  2010.  Changes  in  the  Timing  of  Snowmelt  and  StreamIlow  in  Colorado:  A  Response  to  Recent   Warming.  Journal  of  Climate  23  (9):  2293–2306.  doi:10.1175/2009JCLI2951.1 45  Reiman,  Bruce  and  Dan  Isaak.  2010.  Climate  Change,  Aquatic  Ecosystems,  and  Fishes  in  the  Rocky  Mountain   West:  Implications  and  Alternatives  for  Management.  General  Technical  Report  for  the  U.S.  Department  of   Agriculture  and  U.S.  Forest  Service  November  2010. 44 46  Ptacek  et  al.  2003. 47  AGCI  2006;  IPCC  2007. 48  See  Chapter  4  sections  on  Ecosystems  and  Public  Health  and  Safety  for  more  on  Iire  risk. 55 weather-related changes. On the other hand, service providers such as lodging operators likely have fewer options to consider when contemplating significant operational changes on the basis of climate and weather patterns. Responses may involve proactive or reactive actions in coordination with broader community planning guidance (e.g., Aspen Area Community Plan) or climate-specific policy actions undertaken independently. Collaborative planning—incorporating broad-based stakeholder involvement—may help to devise responses that address specific concerns, while flexibility in discussion and planning structure accommodates the evolving nature of available climate information and risks. Scientific discussion of climate change impacts typically involves timescales between 30-100 years into the future. However, in our assessment of literature and stakeholder interviews, we found that planning within the recreation and tourism sector, particularly among private enterprise, occurs over much shorter, more near-term timescales. For example, at the Aspen Skiing Company, long term planning consists of capital investment planning typically in 10-year increments for significant investments, such as ski lift development and snowmaking equipment.49 Rafting and fishing guide companies typically respond to conditions at seasonal or day-to-day timescales. One constraint to long-term planning is that operational forecasts of climate or hydrologic conditions are typically unreliable beyond the current water year. While the skill of ski area operators to manage frequently changing forecasts and surprise shifts in weather is a valuable human resource for dealing with change, this embedded culture may lead to somewhat of a barrier when future changes depart from existing ranges of variability and require longer term planning and novel strategies. Overcoming the barrier to thinking long-term may be facilitated by the support of governmental entities, such as the City of Aspen, that have mandates to consider and plan for potential risks to the community over more distant time scales. Scenario planning where specific futures are not predicted but multiple potential outcomes are considered is one approach.50 An example of long range planning is the City of Aspen and Pitkin County’s Aspen Area Community Plan that presents a vision and policies to support community development over a 10-year time span.51 49  Interview  with  Rich  Burkley,  Jan  17,  2014 Peterson,  G.  D.,G.S.  Cumming,  and  S.R.  Carpenter.  2003.  Scenario  Planning :  a  Tool  for  Conservation  in  an   Uncertain  World,  Conservation  Biology  17  (2):  358–366. 50 51  City  of  Aspen  &  Pitkin  County.  2012.  Aspen  Area  Community  Plan.  February  27,  2012.  http:// www.aspencommunityvision.com/media/uploads/FINAL_AACP_2272012_reduced.pdf 56 WATER Water plays a critical role in each of the sectors discussed in this report: it determines ecological success, influences health and safety, drives production of energy, and impacts the economy in a myriad of ways. In Aspen and throughout the West, changes in water supply and demand are already active Water management, a perennial areas of discussion, research, and planning. Locally, challenge in the West, is further studies such as the State of the Roaring Fork Watershed complicated by the prospect of Report and resulting Roaring Fork Watershed Plan have climate change. already explored many of the significant issues and trends affecting local water availability and quality.52 At a state level, Western Water Assessment (WWA) produced a 2014 report for the Colorado Water Conservation Board (CWCB) examining the impacts of climate change in Colorado with a focus on water.53 The CWCB also facilitates roundtable discussions and is involved in the creation of a basin-wide implementation plan that will assess consumptive and non-consumptive water needs in relation to water supply across Colorado’s nine basins.54 The purpose of this section on water is not to reproduce earlier studies or to examine all the numerous and complicated water issues in depth. Rather, the purpose is to highlight potential impacts from climate change on water-dependent resources. This general survey of potential climate-related impacts to the water sector should be considered in the context of numerous ongoing water availability studies and water management planning activities—locally, statewide, and regionally. For example, the City of Aspen water department has commissioned a water 52  Clarke,  S.,  K.  Crandall,  J.  Emerick,  M.  Fuller,  et  al..  2008.  State  of  the  Roaring  Fork  Watershed  Report.  Ruedi   Water  and  Power  Authority  and  Roaring  Fork  Conservancy,  November  2008. 53  Lukas  et  al.  2014 54  A  draft  and  proposed  framework  for  Colorado’s  Water  Plan  can  be  found  at:  http://coloradowaterplan.com. 57 availability study and drafted a water efficiency plan that are intended to explore the issues discussed in this chapter in further detail and specificity. Due to the difficulty of scaling models to address topographic variability in the Colorado Rockies, projections for future precipitation in the Roaring Fork Valley continue to include multiple possibilities, ranging from little or no change to either significant decreases or even increases. Projections for the southwestern U.S. as a region, however, show greater agreement among models and indicate a general decrease in annual precipitation.55 These projections suggest that the southwest area of the United States may become more arid as temperatures increase, snowpack decreases, and runoff dates become earlier. Because of the geographically connected nature of watersheds and existing water law and agreements, such as the Colorado River Compact, precipitation and water availability changes that take place regionally will have a considerable impact locally for water management in the Roaring Fork Valley.56 While future trends for quantity of precipitation in the state of Colorado remain uncertain, trends more confidently indicate that the form in which the precipitation will fall is likely to alter over time. A shift to an increased percentage of precipitation falling as rain rather than as snow is projected both locally and at a regional level, particularly at elevations below 8,200 feet. This is an alteration that, combined with higher temperatures and earlier snowmelt, has the potential to impact groundwater and surface water supplies.57 Pitkin County’s population is expected Additionally, higher average temperatures affect water to increase by more than 50% to 25,229 people by 2025. resources. Streamflow is often used as a proxy measurement for water availability, and research indicates that higher temperatures may directly correlate with lower streamflow. Hydrologic modeling for the gage station at Lee’s Ferry in Arizona showed that for every 1.8°F (1.0ºC) increase in average temperature, streamflow in the Colorado River declines between 3-10%.58 Furthermore, any climate-related shifts in water availability that take place occur within the context of changing human demographics as well. Population growth locally and on the Front Range is anticipated to continue, increasing demand for water and the likelihood of potential water shortages by stretching an already limited resource. According to 2010 data from the state demographer’s office for the state of Colorado, Pitkin County’s population is expected to swell 55  Lukas  et  al.  2014. 56  Vano  et  al.  2014. 57  Ray,  A.,  J.  Barsugli,  and  K.  Averyt.  2008.  Climate  Change  in  Colorado:  A  Synthesis  to  Support  Water   Resources  Management  and  Adaptation.  A  Report  for  the  Colorado  Water  Conservation  Board.  Western  Water   Assessment. 58  Vano  et  al.  2014. 58 from the 2010 population of 17,148 to increase by more than 50% to 25,229 people in 2025.59 The population of Colorado as a whole is expected to grow significantly as well, reaching around 7.1 million residents in the next 16 years.60 Although Aspen sits at the top of the watershed, its water resources are unusual in that demand pulls water in two directions: downstream toward the southwestern states and eastward via diversions to the Front Range. Two of the five largest transmountain diversions in Colorado redirect water from from the Roaring Fork Valley.61 Under conditions typical to the last few decades, spring streamflow of the Roaring Fork and Frying Pan Rivers were reduced by more than half due to diversions alone.62 Diversions are essential for municipal uses and for agricultural production, so drying in the Front Range of Colorado and across the Southwest would doubly place pressure on local water availability from the standpoint of demand. Impacts  to  snowpack  and  the  water  cycle   A 2014 report produced for the Colorado Water Conservation Board (CWCB) found that since the 1980s onset of snowmelt has shifted earlier in the year by 1-4 weeks and is projected to continue shifting to earlier in the year in the future as a response to warming temperatures.63 The CWCB’s previous 2008 report64 found that between 2000 and 2004, the Colorado River experienced its lowest 5-year flow since records began in the early 1900s, and hydrologic studies project that low flows may continue as a result of declining runoff—as much as a 6-20% decrease from 20th century averages in the Colorado River Basin. The cited drivers for this decline are increased drought severity in the Western US and high temperatures exacerbated by decreases in soil moisture.65 On a local level, records from the USGS Glenwood Springs gage station show that from 1981 to 2012, peak flow showed a decline of 722 cubic feet per second (see Figure 2.9). Peak flow, the quantity of water in the river on the date of its highest flow of the year, is often considered to be indicative of of depth of snowpack for the preceding winter in snowpack dominated watersheds. Because the Roaring Fork is a heavily diverted river, the observed decline is more indicative of 59  DeGroen,  Cindy.  2012.  Population  Forecasts  (Presentation).  State  Demography  OfIice  Annual  Meeting,   Colorado  Department  of  Local  Affairs,  Nov. 60  Clarke  et  al.  2008. 61  More  information  available  through  the  Roaring  Fork  Watershed  at:  www.roaringfork.org/sitepages/ pid170.php 62  Clarke  et  al.  2008. 63  Lukas  et  al.  2014. 64  Ray,  A.,  J.  Barsugli,  and  K.  Averyt.  2008.  Climate  Change  in  Colorado:  A  Synthesis  to  Support  Water   Resources  Management  and  Adaptation.  A  Report  for  the  Colorado  Water  Conservation  Board.  Western  Water   Assessment. 65  Lukas  et  al.  2014. 59 ongoing diversions to the Front Range than it is of local snowpack conditions. Local snow water equivalent (a proxy of snowpack) has not decreased sharply since 1981 (see Figure 4.1). As discussed in Chapter 2, precipitation and snowfall within the Aspen area have been variable over the period of their observation from 1940-2013. Since 1981, both the data records for precipitation and snowfall have suggested slight decline, although both were increasing in the period before 1980 and the extraordinary winter of 1983/1984 skews the trend analysis (Figures 2.7 and 2.8). As temperatures continue to rise, though, duration of snowpack and percent of precipitation falling as snow rather than rain may decline. Depth of snowpack and duration of snow cover are linked closely to watershed functions, winter ecology, and water availability. Particularly in snowpack-driven watersheds, early snowmelt or low snowpack during winter months can decrease soil moisture levels throughout the following summer, affecting plant growth and stress.66 In addition to the ecologic changes associated with changing water regimes, water availability forms a critical component of the structure of all other systems in the Valley. Human activities as diverse as production of energy or summer water sports are dependent upon sufficient flows. Figure 4.1 Snow water equivalent on April 1 since 1981 Figure 4.1 shows snow water equivalent (SWE) on April 1st in inches from 1981-2013. The blue line shows SWE for each year, and the orange line represents the overall trend of the data. The graph was created using NRCS data from the SNOTEL site on Independence Pass at 10,600ft. 66  Clow,  David  W.  2010.  Changes  in  the  Timing  of  Snowmelt  and  StreamIlow  in  Colorado:  A  Response  to   Recent  Warming.  J.  Climate  23:  2293–2306.  doi:  http://dx.doi.org/10.1175/2009JCLI2951.1 60 Winter recreation is tied closely to snowfall and duration of snowpack. Public health relies upon the assurance of water quality and availability, as do many aspects of our built environment and agriculture and local food production. Public uses, from municipal water supply and wastewater treatment plants to city parks and golf courses, rely upon water being available at critical times of the year. Response  strategies   Building climate resiliency in the water sector requires the consideration of many environmental, societal, legal, and ecological factors such as total annual precipitation, percent rain vs. snow, increases in temperature, soil moisture, population, and societal uses of and allocations for water. Box 4.2 Water summary Climate-related changes: • Increased dry periods in the western U.S. • Decrease in percent of precipitation falling as snow • Changes to the timing and availability of water Future Potential Impacts • Greater pressure on existing water resources • Changes to ecological regimes; decreased soil moisture, lower river flows • Increased risk of fire • Changes to timing and volume of peak flows • Reduced hydroelectric generating potential • Local population growth leading to increased municipal and recreational demand for water Potential Responses • Anticipatory planning and adaptation for multiple climate scenarios • Increased water use efficiency • Development of adaptive plans for ecological impacts • Education and public outreach • Stakeholder involvement in discussion and adaptive planning Opportunities • Renewed consideration of current water allocations, rights, and laws Lingering Uncertainties • Future trends in precipitation • Seasonality of temperature changes in mountain climates under climate change • Future population growth and water demand 61 Potential types of adaptation in the water sector include: Enhanced education and public outreach Local and regional research, monitoring, planning, and investment Ecological restoration and conservation • • • Activities of this sort are underway—and have been for many years— both locally and statewide, but they are now needing to integrate new shifting hydrologic conditions resulting from climate change. The Roaring Fork Watershed Action Plan recognizes the need and has considered climate change into actions proposed.67 For Colorado, Governor Hickenlooper requested a State Water Plan be adopted that recognizes key issues such as population, the Colorado Compact, and climate change. All of these efforts are conducted in the context of existing policies and legal structures that could potentially evolve in the future. 
 67  Clarke,  S.,  M.  Fuller,  and  R.A.  Sullivan.  2012.  Roaring  Fork  Watershed  Plan.  Retrieved  from  http:// www.roaringfork.org/sitepages/pid175.php 62 ECOSYSTEMS As of 2014, climate trends for the Roaring Fork Valley continue to follow the paths outlined in the 2006 report, with a growing number of frost free days and climbing average temperatures. Key ecological findings from the 2006 report remain pertinent. Upward shifts in plant and animal distributions Mountain habitats are comparable to islands in the sense that patches of equivalent habitat are isolated from one another. Both plant and animal species adapted to alpine ecosystems are vulnerable to climate change because they cannot move to higher elevation in response to warming temperatures.68 Research published since 2006 continues to point to vulnerabilities in some alpine species native to the Aspen area, including the white-tailed ptarmigan, which may decline or even become locally extinct as a consequence of shifting climate conditions.69,70 Climate alterations may also cause species shifts or loss through alterations such as changes in form of annual precipitation (rain vs. snow), increases in temperature, or decreases in snowpack that may decrease winter soil temperatures critical to winter ecology. Such alterations can also impact the success of plant communities, causing shifts that cascade up the entire food 68  Olson,  David,  Michael  O'Connell,  Yi-­‐Chin  Fang,  Jutta  Burger,  Richard  Rayburn.  2009.  Managing  for  Climate   Change  within  Protected  Area  Landscapes.  Natural  Areas  Journal  29  (4):  394-­‐399. 69  Imperio,  S.,  R.  Bionda,  R.  Viterbi,  A.  Provenzale.  2013.  Climate  Change  and  Human  Disturbance  Can  Lead  to   Local  Extinction  of  Alpine  Rock  Ptarmigan:  New  Insight  from  the  Western  Italian  Alps.  PLoS  ONE  8  (11):   e81598.  doi:10.1371/journal.pone.0081598 70  Beever,  E.  A.,  C.  Ray,  J.L.  Wilkening,  P.F.  Brussard,  and  P.W.  Mote.  2011.  Contemporary  climate  change  alters   the  pace  and  drivers  of  extinction.  Global  Change  Biology  17:  2054–2070.  doi:  10.1111/j. 1365-­‐2486.2010.02389.x 63 chain.71,72 As conditions become sub-optimal for current plant communities, ecosystems in the Aspen area may transform to resemble communities currently found in lower, warmer conditions present in the mid-valley region and encroachments by invasive species may occur. Poten`al  for  pest  outbreaks  in  forest  ecosystems   Among pest outbreaks currently of high concern for Aspen is invasion by the spruce beetle. Within the Roaring Fork Watershed, 20% of forest type is spruce-fir forest (as compared to only 9% lodge pole pine).73 In 2012 and 2013, the Colorado Forest Insect and Disease Update cited spruce beetle as “the most damaging native forest insect pest” for the state, with spruce beetles infesting 398,000 acres of Colorado spruce forest in 2013.74 Climate change may increase tree susceptibility to disease or infestation as changes in disturbance regimes, temperature, and rainfall weaken resilience of native tree species. Furthermore, proliferation of pests like spruce beetles increases with rising average temperatures. Warmer spring and summer temperatures accelerate the life cycle of spruce beetles, allowing for more rapid development from pupa into adults and a rapid increase in population growth. Although still an active area of research, there is some early indication that winter temperatures that do not dip below -25°F (-32ºC) or -15°F (-26ºC) may allow greater over-winter survival of the larvae and adult beetles, respectively.75 Risk  of  increased  forests  fire  size  and  frequency   In addition to susceptibility to insect invasion, forests in the Aspen area may also be vulnerable to alterations in fire regime as a consequence of climate change. Increased temperatures, decreased precipitation, earlier snowmelt, or increased presence of deadwood from insect outbreaks all raise risk of fire outbreak. 71  Inouye,  David  W.  2008.  Effects  of  Climate  Change  on  Phenology,  Frost  Damage,  and  Floral  Abundance  of   Montane  WildIlowers.  Ecology    89:  353-­‐362.  Available  at:  http://dx.doi.org/10.1890/06-­‐2128.1 72 Parmesan, C. 2006. Ecological and Evolutionary Responses to Recent Climate Change. Annual Review of Ecology, Evolution, and Systematics 37 (1): 637–669. doi:10.1146/annurev.ecolsys.37.091305.110100 73  Meddens,  A.J.H.  and  J.  A.  Hicke.  2013.  Forest  Condition  and  Forest  Disturbance  Metrics  for  the  Roaring  Fork   Watershed,  Colorado:  A  report  for  the  Aspen  Global  Change  Institute.  Department  of  Geography,  University  of   Idaho.  July  26. 74  2013.  Colorado  Forest  Insect  and  Disease  Update:  A  Supplement  to  the  2013  Report  on  the  Health  of   Colorado’s  Forests.  Colorado  State  Forest  Service.  Available  at  http://csfs.colostate.edu/pdfs/2013FHR-­‐ InsectDiseaseUpdate.pdf 75  Jenkins,  Michael  J.,  Elizabeth  G.  Hebertson,  and  A.S.  Munson.  2014.  Spruce  Beetle  Biology,  Ecology  and   Management  in  the  Rocky  Mountains:  An  Addendum  to  Spruce  Beetle  in  the  Rockies.  Forests  5  (1):  21-­‐71. 64 Figure 4.2 Incidence & extent of fires in the Roaring Fork Valley Figure 4.2 shows fires in the Roaring Fork Valley since 1975. The size of each circle represents the relative size of the fire, and the number beside each circle indicates the number of acres that were burned. Data source: White River National Forest. In recent decades, a prior history of fire suppression and subsequent build-up of fuel, combined with climactic change and human activities, have contributed to an increase in size and severity of wildfires in the American West.76 In 2013, in the course of one month alone (June-July), more than 14 fires broke out in the state of Colorado. Furthermore, in part due to expanding exurban development, the fires of the last decade have been record-breaking in their destruction. The Fourmile Canyon Fire in 2010 destroyed 169 homes. In 2012 the High Park Fire destroyed 259 homes. Later that year the Waldo Canyon Fire burned 18,000 acres and consumed 346 homes. In 2013, 486 homes were lost in the Black Forest Fire.77 Previous to 2000, the six most destructive fires in Colorado history destroyed fewer than 20 homes on average. For comparison, the largest fire near Aspen in the last 35+ years has been 2,603 acres, less than 1/6th the size of the Waldo Canyon Fire (see Figure 4.2). 76  Marlon,  Jennifer  R.,  Patrick  Batlein,  Daniel  G.  Gavin,  Colin  J.  Long,  et  al..  2012.  Long-­‐term  perspective  on   wildIires  in  the  western  USA.  PNAS  109  (9):  E535-­‐E543.  doi:  10.1073   77  Voiland,  Adam.  2013.  Nov.  8,  2013  Image  of  the  Day.  NASA  Earth  Observatory.  Available  at       http://earthobservatory.nasa.gov/IOTD/view.php?id=82321 65 While high temperatures and drought conditions have contributed to the growth of these fires, a growing wildland-urban interface and the spread of development have also been cited as key factors driving the spike in property loss associated with Colorado’s recent disasters.78 The Aspen area includes many houses and developments situated in or near forested areas, and an outbreak of a wildfire in the Aspen area could have considerable economic, health and safety, and recreational impacts. Unsuppressed, fires tend to occur on a cyclical basis, with differing return intervals for different forest types, but higher temperatures or dry conditions increase chances of fire outbreak and create potential for fires to be larger and more intense. Years with early snowmelt have been found to have five times as many fires as years with average snowmelt dates. Early snowmelt and runoff (and subsequent soil drying), combined with high temperatures, are projected to contribute to a 74-118% increase in wildfires in Canada within the next 100 years, with similar increases in the western United States.79 The 2006 City of Aspen report provides a more complete discussion of fire risk in relation to different fire suppression scenarios, available fuel, and climate change. Response  strategies   Options for adapting to shifts in the local ecological communities can be grouped into three management approaches: • • • Allowing changes to occur without attempting to promote existing species over new species that may migrate into the ecosystem as warming occurs. Management would focus on passive study and monitoring of how these changes impact broader systems within the watershed. Conservation, where management supports specific species survival by working to preserve key habitats that are highly vulnerable to climate change. Additionally, corridors between comparable habitats might be created.80 Promoting specific species via introduction of species to areas where projected future conditions will meet habitat needs. Species selected might be either species listed as currently threatened or those likely to become well adapted to future climate conditions. 78  Syphard,  Alexandra  D.,  Avi  Bar  Massada,  Van  Bustic,  and  Jon  E.  Keeley.  2013.  Land  Use  Planning  and   WildIire:  Development  Policies  InIluence  Future  Probability  of  Housing  Loss.  PLOSONE  (Aug.  14).  doi:   10.1371/journalpone.0071708 79  Running,  Steven  W.  2006.  Is  Global  Warming  Causing  More,  Larger  WildIires?  Science  313  (5789):  927-­‐928.   doi:  10.1126/science.  1130370 80  Olson,  David, Michael  O'Connell, Yi-­‐Chin  Fang, Jutta  Burger,  and Richard  Rayburn.  2009.  Managing  for   Climate  Change  within  Protected  Area  Landscapes.  Natural  Areas  Journal  29  (4): 394-­‐399. 66 Box 4.3 Ecosystems summary Climate-related changes • Increase in length of frost free period • Alterations to the timing and type of precipitation • Increasing annual and seasonal temperatures • Alteration to snowpack quantity, areal coverage, timing of snowmelt onset and rate of melt Future Potential Impacts • Plant communities shift to higher elevations • Local specialist species may diminish or disappear • Increased likelihood of encroachment by invasive species • Increased conditions for insect outbreaks • Increase in factors contributing to wildfire incidence, intensity, and size • Changes to local ecosystems types • Local extinction of some alpine species • Alterations to water quality or groundwater Potential Responses • Creation of migration corridors • Reduction of human-related stressors on critical wildlife and habitat • Identification and protection of priority species • Collaborative, landscape scale forest management planning • Public outreach and education about changes to ecosystems Opportunities • Potential re-establishment of natural fire ecology for some systems • Collaborating with US Forest Service and Department of Parks and Wildlife on understanding changes to winter ecology Lingering Uncertainties • Future trends in precipitation • Seasonality of temperature changes in mountain climates under climate change • Forest response to potential management regimes • Ecological resilience and ability to adapt to projected changes • Ecosystem response to various potential restoration and management strategies Either a species-specific or a broad, ecosystem-level approach may be taken when considering the best ways to preserve treasured natural assets. Regardless of strategy adopted, management plans and decision-making can be strengthened through a strong research base that identifies potential risks, trade-offs, and consequences of management options in relation to 67 a variety of climate scenarios.81 Adaptive forest management may likewise benefit from analysis of multiple potential scenarios and prioritization of goals or critical habitats. Millar et al. offer three ways to think of adaptive planning for forests: “Resistance” (plans that work to diminish or prevent climate impacts) “Resilience” (strategies to enhance an ecosystem’s ability to rebound after disturbance) “Response” (strategies that “facilitate transition of ecosystems from current to new conditions)82 • • • For example, diversity in tree species offers natural resilience and resistance to host-specific pest outbreaks, but resistance can also be encouraged by management. Studies on outbreaks of pine beetles in the Canadian Rockies suggest that impacts of pests may be further mitigated by identification and targeted harvesting of high risk stands of trees and by management plans for control, salvage, and prevention of beetle outbreaks.83 Community outreach can also provide an important form of risk reduction. The Colorado Wildfire Risk Assessment Portal provides mapping and information about high fire risk areas, and the State of Colorado, among others, encourages development of community wildfire protection plans that include forest management plans and strategies for coping with new and existing development within forest areas. These responses includes: revising building codes, providing public education about defensible space, and developing plans for evacuation, many of which are already being implemented by the Aspen Fire Protection District.84 As humans increasingly live in and near forested areas, ecological plans will need to continue to overlap with social and structural planning and take into consideration desired human interactions, physical structures involved in encroachment, and associated laws and regulations. It may be particularly important locally that adaptive strategies consider ecological objectives within the context of other sectors. Examples for an integrative approach exist, as is demonstrated by action plans such as the Hunter Creek-Smuggler Mountain Cooperative Plan, which draws together a variety of stakeholders and identifies goals that range from biological to educational to economic in nature. 81  Turner,  B.L.,  Roger  E.  Kasperson,  Pamela  A,  Matson,  James  .J  McCarthy,  et  al..  2003.  A  framework  for   vulnerability  analysis  in  sustainability  science.    Proceedings  of  the  National  Academy  of  Sciences  of  the  United   States  of  America. 82  Millar,  C.I.,  N.L.  Stephenson,  and  S.L.  Stephens.  2007.  Climate  change  and  forests  of  the  future:  managing  in   the  face  of  uncertainty.  Ecological  Applications  17  (8):  2145-­‐2151. 83  Schneider,  Richard  R.,, Maria  Cecilia  Latham, Brad  Stelfox, Dan  Farr,  and Stan  Boutin.  2010.  Effects  of  a   Severe  Mountain  Pine  Beetle  Epidemic  in  Western  Alberta,  Canada  under  Two  Forest  Management  Scenarios.   International  Journal  of  Forestry  Research  2010.  http://dx.doi.org/10.1155/2010/417595  WildIire  Mitigation  Webpage.  Colorado  State  Forest  Service,  Colorado  State  University.  Last  updated  2013.   http://csfs.colostate.edu/pages/wildIire.html 84 68 PUBLIC  HEALTH  &  SAFETY   The 2006 Study did not provide a direct, in-depth discussion of the impacts of climate change to public health and safety, but general assertions made, such as the danger of wildfires to human health, still hold true. This 2014 report provides a preliminary assessment of potential impacts to human health and safety in the Aspen area as a result of climate change, though more detailed assessment based on site specific conditions and vulnerabilities is still needed. Aspen’s elevation and geographic location will likely serve as an important source of protection against some anticipated health impacts associated with climate change. Aspen is not immune to all potential risks, however. Some risks, such as wildfires, landslides, or deterioration of air quality, may have direct impacts on the health and safety of visitors and residents of Aspen. Other threats may be more indirect, such as increased anxiety about the state of the environment or altered mobility or economic stability of potential visitors to Aspen85. Visitors and locals alike would both be at risk in the case of catastrophic events, such as landslides or fires. While fires are an important natural cycle for ecosystems, they also pose serious threats to human health: loss of property and risk of direct physical harm and increase potential for related floods or landslides. With a large proportion of Aspen’s population living and recreating in or near forested areas, potential health and safety consequences for Aspen from wildfires are considerable. In the western United States, the active wildfire season has increased by 78 days over the last century, and the odds of increasingly large or intense wildfires are anticipated to rise in the future.86 85  Melillo,  Jerry  M.,  Terese  (T.C.)  Richmond,  and  Gary  W.  Yohe,  Eds.  2014.  Climate  Change  Impacts  in  the   United  States:  The  Third  National  Climate  Assessment.  U.S.    Global  Change  Research  Program:  841.  doi: 10.7930/J0Z31WJ2.    Running,  Steven  W.  2006.  Is  Global  Warming  Causing  More,  Larger  WildIires?  Science  313  (5789):  927-­‐928.   doi:10.1126/science.1130370 86 69 Decreased  air  quality   Recent findings suggest that in addition to increased fire risk, the warmer temperatures associated with climate change may also have impacts on air quality. The early onset and greater duration of the growing season may increase the length of the allergy season, while CO2 fertilization may increase pollen and spore production, worsening allergies for those with hay fever.87 Additionally, hot days often correlate with higher levels of ground-level ozone, so an increasing number of warm days could mean more frequent days with ozone levels above those considered healthy. Ozone is an oxidant and at high concentrations reacts with human tissue. High levels of ozone can irritate lung tissue, aggravate pre-existing respiratory conditions, and may contribute to increased likelihood of respiratory infections.88 Changes in temperature and precipitation regimes could have a significant impact on the spread of disease, even for high altitude locations. Aspen’s recent ozone levels (2013) have been below the EPA standard of 75 parts per billion, but high temperatures correlate with higher levels of ground-level ozone, so as temperatures rise, ozone levels throughout the summer months may also increase. 89 Fine airborne particulate matter can also pose respiratory risks. Impacts of climate change on aerosols and particulate matter are still not fully understood, but increased incidence of fires would increase both. Further, changes in wind or weather patterns could change global distribution of pollution from transportation and industry as well as wind borne mineral dust from mining, fossil fuel extraction and recreation particularly from upwind desert areas to the west — all important source of particulates. Particulate pollution from combustion is released by hightemperature industrial processes, wildfires, gasoline and diesel engines, and during the production of fossil-based power.90 Although the City of Aspen Electric system is on its way to  Frumkin,  Howard,  Jeremy  Hess,  George  Luber,  Josephine  Malilay,  and  Michael  McGeehin.  2008.  Climate   Change:  The  Public  Health  Response.  American  Journal  of  Public  Health  98  (3):  435-­‐445.  doi:    10.2105/AJPH. 2007.119362 87 88  Climate  Impacts  on  Human  Health.  Human  Health  Web  Page.  Last  updated  Sept.  2013.  Environmental   Protection  Agency.  Available  at  http://www.epa.gov/climatechange/impacts-­‐adaptation/health.html 89  Aspen/Pitkin  County  Website.  Data  available  at:  http://www.aspenpitkin.com/Departments/ Environmental-­‐Health/Air-­‐Quality-­‐Outdoors/Ozone/Historical-­‐Ozone-­‐Levels/ 90  Climate  Impacts  on  Human  Health  2013 70 achieving 100 percent of its electricity from renewables, pollution from far away sources and, locally, its busy streets will continue to affect Aspen air quality.91 Figure 4.3 Projected probability of presence of West Nile Virus Figure 4.3 Probability of presence of West Nile virus (WNV) projected for the years 2050 and 2080 under the A1B middle emissions climate scenario. Areas in red indicate increased probability of WNV presence by at least 10% compared to current incidence. Areas in blue represent decreased predicted prevalence. Source: Harrigan et al. 2014. Vector borne disease As temperatures shift across the United States, so too will the range of animal species that are vectors for disease. As temperature and moisture regimes change, so too might the prevalence of carrier species, such as the birds and insects spreading vector borne diseases such as West Nile Virus (WNV). The Center for Disease Control reports that there were 318 cases of WNV and 7 WNV-related deaths reported for Colorado in 2013.92 A recent study by Harrigan and colleagues found a strong correlation between prevalence of West Nile Virus and higher temperature/lower  Frumkin,  Howard,  Jeremy  Hess,  George  Luber,  Josephine  Malilay,  and  Michael  McGeehin.  2008.  Climate   Change:  The  Public  Health  Response.  American  Journal  of  Public  Health.  98(3),  435-­‐445.  doi:    10.2105/AJPH. 2007.119362 91 92  Data  available  at:  http://www.cdc.gov/westnile/statsMaps/preliminaryMapsData/histatedate.html 71 precipitation regimes.93 As a result, climate variables can be used to project the probability of the presence of West Nile Virus (WNV), where higher maximum temperatures in the warmest month lead to higher probability of virus presence. Seasonal drying and lower annual precipitation were also associated with higher likelihood of outbreaks over the next 50-80 years. Harrigan et al also found that the geographic distribution of WNV was expected to shift northward and up in altitude with climate change, increasing probability of WNV by 2050 for the Rocky Mountain Region of Colorado, including high altitude locations (see Figure 4.3).66 The shift to warmer temperatures may also lead to an upward movement in the distribution of invasive mosquito species, including those typically associated with tropical habitats and tropical disease. Changes in land use, socio-economic conditions, human behavior, population density, and water use all may additionally play a role in prevalence and spread of transmission of vector borne diseases.94 The presence of a disease such as WNV in the Aspen area could have significant negative impact on local bird populations and could pose a direct threat to human health. Other potential threats to public health and safety include: mental health concerns, changes in food and water supply stability, and increased pressure on resources as a consequence of population increase. For example, climate change may impact mental health in the form of anxiety over associated environmental degradation or stress in relation to a climate driven disaster, such as a wildfire.95 Additionally, both local and non-local food production may shift in relation to changes in climate patterns, water availability, and disruptions to global food markets. Response  strategies   Outreach, development of appropriate codes, increasing response capacity, identification of high risk locations, and structural changes are all potential strategies for adaptively managing climate-related risks to public health and safety. Building codes and conscientious development planning are key to helping prevent disasters such as fires or flooding and can assist in avoiding development of mosquito-prone areas. Distribution of information can also help to ameliorate the health risks associated with climate change. Public education and outreach, particularly for tourists, can help to prevent illnesses  Harrigan,  Ryan  J.,  Henri  A.  Thomassen,  Wolfgang  Buermann,  and  Thomas  B.  Smith.  2014.  A  continental  risk   assessment  of  West  Nile  virus  under  climate  change.  Global  Change  Biology.  John  Wiley  and  Sons,  Ltd.  doi:   10.1111/gcb.12534 93  Harrigan,  Ryan  J.,  Henri  A.  Thomassen,  Wolfgang  Buermann,  and  Thomas  B.  Smith.  2014.  A  continental  risk   assessment  of  West  Nile  virus  under  climate  change.  Global  Change  Biology.  John  Wiley  and  Sons,  Ltd.  doi:   10.1111/gcb.12534 95  Melillo,  Jerry  M.,  Terese  (T.C.)  Richmond,  and  Gary  W.  Yohe,  Eds.  2014.  Climate  Change  Impacts  in  the   United  States:  The  Third  National  Climate  Assessment.  U.S.    Global  Change  Research  Program:  841.  doi: 10.7930/J0Z31WJ2.   94 72 such as heat stress. Education can also play a role in disaster readiness. It can help to build compliance with laws and regulations and can encourage preparedness at a family level. For example, the Center for Disease Control promotes creation of escape plans and disaster kits in every home.96 Finally, promoting enhanced response capacity can improve community ability to meet a variety of as-of-yet uncertain health concerns. For example, health care providers may evaluate the Box 4.4 Health and safety summary Climate-related Changes • Increased frequency of extreme high temperatures • Increased risk of extreme events (e.g. drought, fire, flood, landslide) • Increased presence of particulate matter and tropospheric ozone • Changing ranges of disease-carrying species • Changing climate conditions affecting food supply Future Potential Impacts • Environmental stress-related mental illnesses • Increased respiratory illnesses as a result of air quality impairment • Increased incidence of vector borne diseases • Loss of property or injury related to disaster events • Lengthened and intensified allergy season Potential Responses • Assessment of high risk populations • Address pre-existing local health concerns • Prioritize potential threats to public health and safety in relation to existing capacities • Assess and improve building codes and regulations in relation to changing hazards • Public education and outreach • Assess and improve early warning systems Lingering Uncertainties • Exposure of Aspen to vector borne diseases and other climate-related health risks • Management impacts on wildfires • Public response to changes • Alteration of prevailing wind patterns • Alteration of air quality from regional fossil energy extraction and production CDC’s  Building  Resilience  Against  Climate  Effects  (BRACE)  Framework.  Climate  and  Health  Program   Webpage.  Last  updated  2012.  Centers  for  Disease  Control  and  Prevention.  Available  at  http://www.cdc.gov/ climateandhealth 96 73 vulnerability of local populations to respiratory illnesses or illnesses such as WNV and create plans accordingly. Outreach and education may also promote health and safety by improving compliance with regulations and creating a sense of community involvement, leading to empowerment and diminishing stress and uncertainty. 
 74 ENERGY Energy use is tightly coupled with the climate challenge, both in terms of mitigation and adaptation. Emissions of greenhouse gasses from fossil fuels are the single largest contributor to anthropogenic climate change, and the impacts of climate change on the energy sector are anticipated to significantly affect the supply of and demand for energy at global and local scales. Options for reducing the carbon intensity of energy include increased utilization of renewables, which rely on variable resources such as sunshine, wind, or water. The impacts of climate change on energy were not explicitly considered within the scope of the 2006 Study, but much of the climate and hydrological analysis from that study is pertinent to the assessment of impacts to Aspen’s future energy supply and demand.97 Factors such as changing normal and extreme temperatures, changing precipitation, and alterations to the timing and magnitude of stream flow carry ramifications for the resiliency of Aspen’s energy supply. These factors may also influence ability to meet desired reductions in greenhouse gases as stated in the Climate Action Plan.98 Electricity  supply  implica`ons   Renewable, low carbon energy sources rely heavily upon fluctuating natural resources such as moving water, wind, or solar radiation. As a result, renewable energy is in general more affected by change in weather or climate than fossil-based resources.99 Aspen’s energy supply is 97  See  chapters  2  &  6,  AGCI  2006. 98  City  of  Aspen  Canary  Initiative.  2007.  Climate  Action  Plan.  City  of  Aspen.  Available  at   http://www.aspenpitkin.com/Portals/0/docs/City/GreenInitiatives/Canary/CAP-­‐Iinal%20without %20dates.pdf     99  Bureau  of  Reclamation.  2013.  Literature  Synthesis  on  Climate  Change  Implications  for  Water  and   Environmental  Resources.  Technical  Memorandum  86-­‐68210-­‐2013-­‐06.  Denver,  CO.  Available  at  http:/ www.usbr.gov/climate/docs/ClimateChangeLiteratureSynthesis3.pdf 75 particularly exposed to potential changes in climate and hydrology because a significant portion of the City of Aspen’s electricity supply100 comes from snowpack-dependent river flows and reservoir storage that generate power through hydroelectric facilities, such as Ruedi Reservoir (see Figure 4.4).101 In general, climate-related issues that concern hydropower generation include water quantity and quality, temperature-related stresses, and operational impacts due to extreme weather.102 Another interesting factor linking Aspen’s energy to global trends and climate change mitigation is the emergence of electric vehicles and the potential to shift Figure 4.4 City of Aspen utility away from gasoline to electric vehicles. This may transfer a greater proportion of Aspen's electricity sources (2013) energy consumption to electricity in the coming decades. At Ruedi Reservoir, the reservoir level, which is significantly affected by winter snowpack, is a key factor in energy production, along with other management concerns such as water rights, upstream diversions on the Frying Pan, recreational needs for the reservoir, water temperature for the Frying Figure 4.4 provides a snapshot of electricity sources Pan fish ecology below the dam, and flood for the City of Aspen Electric system in 2013. The composition of energy sources vary from year to management. Figure 4.5 characterizes the year based on climate conditions and purchasing relationship between winter snowpack agreements. For instance, the portion of City of measured at the Kiln SNOTEL station on Aspen electric supply from hydro for 2014 is April 1st and the annual electricity production expected to be 37%, as compared to the 25% generated by Ruedi. Although numerous shown above. Source: City of Aspen. variables play a role in water management and electricity production at Ruedi, there is a clear relationship between local snowpack and electricity production. This vulnerability is addressed to some extent by the existing diversity—both in location and type—of Aspen’s electric supply mix and the ability to acquire sources outside the Roaring Fork Valley, but the correlation between snowpack and energy production highlights the potential for extreme conditions such as drought to alter renewable energy production on a year-to-year basis. 100  This  considers  only  electricity  supply  provided  by  the  City  of  Aspen  operated  electric  utility  and   not  the  portion  of  electricity  supplied  to    Aspen  by  Holy  Cross  Energy. 101City  of  Aspen-­‐100%  Renewable  Power  by  2015.  Go  100%  Renewable  Energy  Web  Page.  Renewables  Policy   100  Institute.  Available  at  http://www.go100percent.org. 102  Bull,  S.R.,  D.E.  Bilello,  J.,  Ekmann,  M.J.  Sale,  and  D.K.  Schmalzer.  2007.  Effects  of  climate  change  on  energy   production  and  distribution  in  the  U.S. Effects  of  Climate  Change  on  Energy  Production  and  Use  in  the  U.S.:  A   report  by  the  U.S.  Climate  Change  Science  Program  and  the  subcommittee  on  Global     Change  Research.  Washington,  D.C. 76 Over the long term, climate change may have a major effect on electric production for the Upper Colorado River Basin, affecting reservoirs such as Ruedi. While interannual precipitation amounts vary greatly year to year, trends in maximum SWE and total annual precipitation since 1981 above Ruedi Reservoir are relatively flat based upon the Kiln SNOTEL site data. If precipitation remains about the same as recent decades, rising temperatures will still alter runoff. Model estimates show that for a 1.8ºF (1.0ºC) increase in temperature there is about a 3% to 10% decrease in runoff.103 Other model analyses indicate the importance of precipitation as well: for a 10% reduction in precipitation there is a corresponding 20% reduction in runoff. In this work, estimates for the Upper Basin in the case of a 2ºC increase in temperature by 2050 indicate a decrease in runoff on the order of 4-18%. These long-term effects, coupled with annual and inter-annual variability, will offer new challenges to hydroelectric managers.104 Figure 4.5 Electricity production and snowpack above Ruedi Reservoir Figure 4.5 shows annual electricity production at Ruedi Reservoir alongside snow water equivalent measurements taken on April 1 each year at the Kiln SNOTEL monitoring site. Although the April 1st measurement is only a proxy for Ruedi reservoir water supply, the correlation between annual production and April snowpack highlights the connection between climate variability and renewable energy production in the Roaring Fork Valley. Source: NRCS SNOTEL and City of Aspen. 103  Vano  et  al.  2014 104Hoerling, M., D. Lettenmaier, D. Cayan and B. Udall. 2009. Reconciling Projections of Colorado River Streamflow. Southwest Hydrology 31. 77 Energy  demand  implica`ons   Aspen’s changing climate will affect the nature and timing of energy demand, particularly the heating and cooling demand in area buildings. The following subchapter on infrastructure and the built environment presents projections for heating and cooling degree days by mid-21st century. Since energy for cooling is predominantly provided by electricity, whereas energy for heating is mainly provided by natural gas, both the timing and overall annual electricity demand will change. Rising temperatures lead to more cooling days, which in turn means a rise in summer electricity demand. This shift in the nature of energy demand, along with anticipated increases in population, places an even greater burden on regional and municipal efforts to reduce energy demand through efficiency improvements and to lower the carbon intensity of energy use. Climate risks to national and international energy supply Aspen’s tourism-based economy relies on a national and international energy infrastructure to provide reliable and affordable energy, particularly for the sources utilized to transport visitors by air or ground. In addition to alterations to hydropower production beyond the Roaring Fork Valley, a number of other climate related outcomes may impact global energy supply including:105 • • • Energy production curtailed regionally and nationally due to water, temperature, and supply constraints Direct impact on production due to extreme events Sea level rise damage to existing energy infrastructure and impairment of new energy infrastructure Aspen’s exposure to this impact may be limited due to the affluent profile of visitors coming to Aspen. Many visitors may be able to absorb even significant changes in the price of energy— either at home or for travel—and may also be able to manage short-term drops in energy reliability. Response strategies Responding to the potential impact of climate change on Aspen’s energy resources will require more site-specific study of local energy sources. In addition to potential impacts of climate change on energy supply, changes in timing and in overall quantity of energy demand and nonclimate drivers such as population growth may also be worth consideration. Strategies that 105  USGCRP  2009. 78 Box 4.5 Energy summary Climate-related Changes: • Increasing summertime high temperatures • Warming wintertime minimum temperatures • Alterations to snowpack and timing and quantity of runoff Future Potential Impacts • Uncertainty of future dependability of energy sources, such as hydroelectric • Increase in cooling load and reduction in heating load demand in buildings • Climate-related risks to national and international energy supply Potential Responses • Development of site-specific evaluation of energy resource among future climate scenarios • Diversification of location and type of renewables • Integration of demand side management and GHG reduction strategies in energy resiliency planning Opportunities • Code requirements for greater building efficiency, reduced carbon emissions • Reduction in heating degree days and increase in cooling degree days may smooth out annual energy demand curve for Aspen’s utility, currently a “winterpeaking” utility • City of Aspen electric and Holy Cross Energy can incorporate future climate projections in their supply and demand planning, particularly in relation to the anticipated increase in renewable sources • Aging infrastructure replacement can incorporate future climate projections in design standards (road, runway, bridge abutments, power system capacity, etc.) Lingering Uncertainties • System effects of electricity becoming a greater share of total energy supply • Extent of additional annual and seasonal alteration of solar and wind resources • Effect of future trends in precipitation, streamflow, and water storage on hydroelectric potential enhance resiliency may include reducing vulnerability to sudden local changes in climate and hydrological conditions by acquiring a more diverse source of energy production capacity within and beyond the Roaring Fork Valley. The City of Aspen Electric utility has a progressive approach of acquiring a high percentage of its electricity from renewables with the goal of achieving 100 percent. The portion of the upper valley supplied by Holy Cross Energy is operating under the Colorado Renewable Portfolio goals. Both utilities have active programs on the demand side to increase efficiency. In addition, 79 the Community Office of Resource Efficiency provides incentives for renewables combined with audits and efficiency upgrade incentives. Evaluating these programs anew in light of how climate change can affect supply and demand in the coming years will further these programs while building greater resiliency. Under the guidance of the City’s Canary Initiative, a carbon inventory was initiated and subsequently updated. This set of studies points to transportation as the major contributor to Aspen’s total greenhouse gas emissions. On this front, a mass transit bus system (RFTA) has been successful in reducing individual vehicle use and in abating congestion valley-wide; however, in general the fuels component of energy use has been more problematic in achieving overall reductions compared to electricity. Fuels are a global commodity, so the question of reliable fuel supply is tied to how climate change affects global supply. Continued dialog that explores overall valley, community, and neighborhood design, combined with understanding of present and desired social frameworks for lifestyle and work, can alter transportation requirements and potentially reduce present and future dependence on fossil fuels for mobility while reducing vulnerability to external factors in fuel markets. Less research has focused on how climate change will affect the transportation sector than how it will affect electricity supply, but there is ample research on the relationship between climate change and the built environment, particularly in relation to heating and cooling loads — Aspen’s largest source of greenhouse gas emissions after transportation and electricity. 80 INFRASTRUCTURE  &  THE  BUILT  ENVIRONMENT   As average and extreme climate and weather trends continue to change, significant and potentially costly impacts are expected for residential, commercial, and public buildings as well as transportation, utility, and other infrastructures that connect and provide services to the community.106 Design criteria that respond to changing climate-related risks can accrue numerous societal co-benefits, such as improved service reliability, comfort, and public health, while hardening critical assets to extreme weather events.107 Resiliency planning with respect to infrastructure and the built involvement may include the following efforts: • • • Building code review and revision Planning and design of new buildings or infrastructure investments Remodeling or replacement of existing assets Many of the climate change related impacts to the built environment and infrastructure, such as fire, flooding, and landslide, also exist under normal climate conditions, and their importance is already reflected in regional planning documents such as the Pitkin County Pre-Disaster 106  U.S.  Global  Change  Research  Program  (USGCRP).  2009.  Global  Climate  Change  Impacts  in  the  United  States.   (T.  Karl,  J.  Melillo,  &  T.  Peterson,  Eds.).  Washington,  DC.  Http://library.globalchange.gov/products/ assessments/2009-­‐national-­‐climate-­‐assessment/2009-­‐global-­‐climate-­‐change-­‐impacts-­‐in-­‐the-­‐united-­‐states. 107  Younger,  M.,  H.R.  Morrow-­‐Almeida,  S.M.  Vindigni,  and  A.L.  Dannenberg.  2008.  The  built   environment,  climate  change,  and  health:  opportunities  for  co-­‐beneIits.  American  Journal  of  Preventive   Medicine  35  (5):  517–26.  doi:10.1016/j.amepre.2008.08.017 81 Mitigation Plan Update (2012).108 However, climate change will shift the probability of some of these events and warrant further evolution of codes and best practices. Changes  to  hea`ng  and  cooling  requirements   Climate trends in Aspen’s recent past indicate relatively dramatic increases in minimum temperatures on a diurnal and monthly basis, along with an overall gradual increase in average annual temperature (see Chapter 2). Projections for Aspen and the surrounding regions indicate continuation of these trends. One result of these shifts that is relevant to the built environment will be “Infrastructure designed to handle an overall decrease in the heating load requirements past variations in climate can instill a of buildings and an increase in cooling false confidence in its ability to handle requirements.109 future changes.” -U.S. Global Change Research Downscaled climate projections prepared by the Program, 2009 USGS indicate a potential reduction of approximately 1500-2000 heating degree days per year and an increase of cooling degree days by approximately 300 degree days by the middle of the century under high emissions assumptions.110 Figures 4.6a and 4.6b map out these potential changes for Aspen and the surrounding region. For some buildings already equipped with heating and cooling systems, this shift may require only modest adjustment. However, for many Aspen buildings only equipped with heating systems, more days per year with high temperatures above tolerable comfort zones could involve significant capital investment to install cooling systems through retrofit. Although some owners may opt for behavioral changes or the “grin and bear it” approach, facilities designed to accommodate tourists or less adaptable clientele will likely be encouraged to ensure adequate cooling capacity. Smart design utilizing passive heating and cooling with appropriate efficiency attributes of building envelopes, can often achieve the comfort zone desired without additional energy requirements and even achieve energy reductions. 108  Pitkin  County.  2012.  Pre-­‐Disaster  Mitigation  Plan  Update.  04  January  2012.  Available  at  http:// www.dhsem.state.co.us/sites/default/Iiles/Pitkin%20County%204.2006.pdf Bureau of Reclamation. 2013. Literature Synthesis on Climate Change Implications for Water and Environmental Resources. Technical Memorandum 86-68210-2013-06. Denver, CO. Available at http://www.usbr.gov/climate/docs/ClimateChangeLiteratureSynthesis3.pdf 109 110  USGS.  Derived  Downscaled  Climate  Projection  Portal.  Last  updated  April  20,  2014.  http://cida.usgs.gov/ climate/derivative/ 82 Figure 4.6a Projected change in heating degree days Figure 4.6b. Projected change in cooling degree days Figure 4.6a shows change in heating degree days per year for the projection period 2041-2070 using an ensemble of models running on the IPCC SRES A1FI (high) emissions scenario. Pitkin County is outlined in blue. Heating degree days for the area surrounding Aspen are expected to decrease (see color legend for approximate values) relative to 1960-1999 modeled values. The Degree Day Threshold is at 65.0ºF (18.3ºC). Figure 4.6b shows change in cooling degree days per year for the projection period 2041-2070 using an ensemble of climate models running on the IPCC SRES A1FI emissions scenario. Pitkin County is outlined in blue. Cooling degree days for the surrounding area are expected to increase (see color legend for approximate values) relative to 1960-1999 values. Threshold considered is 65ºF (18.3ºC). Source: USGS Derived Downscaled Climate Projection Portal. 83 Figure 4.7a Projected continuous dry days for Pitkin County Figure 4.7b Modeled heavy rain in Pitkin County Figure 4.7a shows an increase in the length of the longest period each year receiving less that 3mm (0.1 inch) of precipitation under a high emissions scenario (A1FI). The average number of modeled dry days per year between 1960-1969 was 38.5. By the middle of the century (2040-2069), projections show this number increasing to 45.7 and by the end of the century (2080-2099) 47.9. Figure 4.7b shows an increase in the number of days receiving greater than one inch of precipitation projected for Pitkin County. Model results present downscaled multi-model CMIP3 data that assess the number of days receiving more than 1 inch of precipitation under a high emissions scenario (A1FI). The average heavy rain days for the modeled period 1960-1969 was 1.7. By the middle of the century (2040-2069), the projected number of days with heavy rain increases to 2.7, and by the end of the century (2080-2099) 3.9. Source: USGS Derived Downscaled Climate Projection Portal. 84 Impacts  from  extreme  events   Aspen’s location alongside the Roaring Fork River, large tracts of forest, and steep hillsides poses significant risk of flood, fire, landslide, and mudflow. Existing pre-disaster planning acknowledges these risks but does not take into account the effects of a future changing climate.111 Assessing the likelihood of future flood and fire risk is confounded by uncertainty in the projection of the magnitude and timing of future hazards, particularly projections of changing extremes in precipitation—or lack thereof—that are most relevant for identifying flood, fire, and landslide risk, in addition to the more prolonged impacts of drought. Modeling products derived from downscaled climate projections under high emissions scenarios project an increased number of days of heavy precipitation as well as longer dry spells with little or no precipitation. These regional model results suggest a shift in the type of extreme climate events Aspen may experience — a shift from what was considered normal during the 20th century. Figures 4.7a and 4.7b project both an increase in the number of heavy rain days and an increase in the duration of consecutive days receiving little (under 3mm) to no precipitation. This finding is consistent with general expectations of climate change where precipitation, regardless of overall quantity, will come less frequently but in heavier amounts. In other words, when it rains, it pours.112 Impacts associated with increased extremes in both dry periods and heavy rain events merits consideration in planning, design, and construction of buildings and infrastructure. In addition to floods, landslides and mudflows, other potentially destructive events associated with extreme precipitation have been identified as a key risk to settlement and society by the IPCC.113 The Aspen area community is situated nearby numerous unstable geologic features such as alluvial fans, rock fall areas, and otherwise unstable slopes.114 Response  strategies Response strategies to climate-related risks posed to infrastructure and the built environment, as in other sectors, may involve a combination of efforts that assess site-specific risks for the purpose of (re)designing assets to reduce exposure or enhance resiliency. Review and reconsideration of existing building, energy, stormwater, and zoning regulations in the context of future climate risks could be one component of this iterative process. 111  Pitkin  County  2012. 112  Madsen,  T.  and  E.  Figdor.  2007.  When  It  Rains  It  Pours  -­‐  Global  Warming  and  the  Rising  Frequency  of   Extreme  Precipitation  in  the  U.S.  Environment  America  Research  and  Policy  Center.  http:// www.environmentamerica.org/uploads/oy/ws/oywshWAwZy-­‐ 113  IPCC  WGII  2007.  WRC  Engineering  Inc.  2001.  Storm  Drainage  Master  Plan  for  the  City  of  Aspen,  CO.  http:// www.aspenpitkin.com/Portals/0/docs/City/engineering/stormwater/  Development/1963-­‐20.pdf 114 85 Box 4.6 Infrastructure & Built Environment Summary Climate-related Changes • Shift in the magnitude of temperature and precipitation extremes • Reduction in wintertime minimum temperatures; increase in maximum temperatures • Alterations in timing of runoff and quantity of run-off Future Potential Impacts • Increase in hazards to structures and infrastructure from flood, fire, and drought • Increase of buildings’ demand in cooling load and reduction in heating load Potential Responses • Evaluation and possible revision of building codes and infrastructure standards that address changing hazard risk • Further evaluation of preparedness and response to low probability, high consequence events (e.g. more catastrophic wildfires) • Integration of resilience and GHG reduction efforts into planning of codes and energy-intensive infrastructure such as transportation Opportunities • Rationale for improved building design requirements; integrating development codes with long term climate mitigation goals • Integrating additional stormwater and mudflow mitigation techniques into urban design projects and parks • New infrastructure engineered for the range of likely future scenarios will be able to be in service longer, have greater resiliency to change, and require lower resource utilization Lingering Uncertainties • How to determine climate change related infrastructure investments compared to best practices based upon historical climate data Collective action with private property owners to assess risk and devise strategies as well as consultation with regional, statewide, and federal agencies and resources may be beneficial in identifying pathways that involve collective action and shared risks. Insight from green infrastructure, architecture, and land planning that account for both environmental hazards to human development and potential impacts on the environment from infrastructure development may lead to more transformational strategies that enhance resiliency, preserve capital investments, and improve well-being and public health. In terms of coming up with adaptive strategies for first-order single stressors such as a prolonged drought, there are often second and third order impacts to consider. With drought 86 there are riparian habitat impacts and increased risk of fire. With fire, there is increased risk to human health and the built environment. Economic effects would include impacts to fishing and rafting recreation, available water for irrigation, etc. These multi-stress situations can have far deeper overall affects on the community and its resiliency when considered in total. Another important factor in adaptation planning is that when climate related impacts fall within a manageable range their impacts are taken in stride with existing systems and responses; however, some impacts do not scale in a linear fashion, but rather reach thresholds which, when exceeded, break down a community’s ability to cope.115 Wilbanks, T.J., P. Kirshen, D. Quattrochi, P. Romero-Lankao, et al.. 2008. Effects of Global Change on Human Settlements. In: Analyses of the effects of global change on human health and welfare and human systems. A Report by the U.S. Climate Change Science Program and the Subcommittee on Global Change Research. [Gamble, J.L. (ed.),K.L. Ebi, F.G. Sussman, T.J. Wilbanks, (Authors)]. U.S. Environmental Protection Agency, Washington, DC, USA: 89–109. 115 87 CHAPTER  5:  STAKEHOLDER  INTERVIEWS   For the purpose of gaining insight from the Aspen community on climate change impacts and potential responses, AGCI and the City of Aspen conducted interviews with 11 local stakeholders. These interviews constituted a preliminary round of engagement, and were intended as a precursor to other future opportunities for community involvement in resiliency plan development. Stakeholders interviewed included City of Aspen and Pitkin County administrators, local business owners, resource managers, conservation planners and advocates, and other professionals working in sectors considered in this study.116 Although the group interviewed represents a selection of local experts with sustained connections to the Roaring Fork Valley and deep involvement with and knowledge of their sectors, some of the observations and perspectives described in the following pages are anecdotal or based on personal opinion.117 During the semi-structured interviews conducted with community members, questions focused on: Existing decision-making and management activities within his/her sector Vulnerabilities within the sector including but not limited to climate change Observations of climate change at a local level and associated impacts • • •  With  thanks  to  the  following  for  participating  in  stakeholder  interviews:  Richard  Burkley  (Aspen  Skiing   Company),  Debbie  Braun  (Aspen  Chamber  Resort  Association),  Steve  Barwick  (City  of  Aspen),  Sharon   Clarke  (Roaring  Fork  Conservancy),  Jeff  Dickinson  (Energy  and  Sustainable  Design  Inc.  and  Biospaces  Inc.),   Mark  Fuller  (Ruedi  Water  and  Power  Authority),  Boots  Ferguson  (Holland  and  Hart),  Bob  Harris  (formerly,   Blazing  Adventures),  Jonathan  Lowsky  (Colorado  Wildlife  Science),  Barry  Mink,  M.D.  (Aspen  Valley   Hospital),  and  Gary  Tennenbaum  (Pitkin  County). 116  Please  note  that  these  descriptions  depict  the  opinions  and  observations  of  individual  stakeholders  and   are  independent  of  Iindings  or  opinions  of  the  Aspen  Global  Change  Institute. 117 88 • • Expectations of future climate change at a local level and anticipated impacts Actions undertaken or contemplated in response to climate change Throughout these interviews, concerns about climate change as well as other challenges such as population growth, development, and economic stability came to the surface. These concerns provided insight into perception of the challenge of climate change in the context of many other competing priorities. As a result, the interviews illuminated opportunities for actions in response to climate change to occur alongside or in support of existing activities and initiatives. Full transcripts of interviews are provided to the City of Aspen as a supplement to this report. Based on the agreement with the interviewees, these transcripts are confidential. Box 5.1 Local changes or impacts identified by stakeholders: • • Changes  observed  in  local  climate   and  associated  impacts   Drought conditions are more common Seasonal weather patterns are less predictable Earlier onset of spring Decreasing winter snowpack Reduction in extreme cold winter temperatures Species shifts in plant and animal communities, especially birds Stakeholders interviewed were asked about changes they have observed that they believe may relate to climate change. All • those who were surveyed were able to • • identify changes they thought were significant, although many were uncertain as • to the extent that the changes were caused by climate shifts. The most common stakeholder observations related to increases in temperature, such as an early onset to spring. Many stakeholders noted that in the past timing and behavior of different seasons were more predictable, but more recently, as one stakeholder described, “The norm is to have dramatic fluctuations.” Some interviewees linked temperature and seasonal shifts to changes in plant or animal behavior and presence in the Aspen area. Other stakeholders noted the implication of a longer summer might have on increasing the season for recreational activities such as mountain biking —opportunities that may pose challenges to protection of natural resources, including wildlife. The second most common observed “There are species that are shifting northward changes were those related to precipitation at the same time that there are species and water availability, such as decreased shifting upward, and there are some species winter snowpack or summer drought that are shifting northward and upward.” conditions. Many stakeholders spoke vividly about the recent 2002, 2011, and 2012 droughts as examples of conditions that may be more frequent in the future. The impacts of 89 droughts were perceived to be far-reaching and included: high fire risk, damages to riparian systems, and alterations to winter and summer recreational amenities such as skiing or rafting conditions. Box 5.2 Actions identified by stakeholders as already in progress: One hopeful observation made by several stakeholders was the expression of a sense that public awareness of climate-related issues has increased over the last decade. Current  &  future  vulnerabili`es   Stakeholders interviewed were asked about current and future vulnerabilities to the sector in which they operate. Across the stakeholders interviewed, many mentioned the same vulnerabilities as a primary concern. • • • • • • Water efficiency planning and riparian health management (e.g. Roaring Fork Watershed Plan) Improved operational speed and flexibility for snowmaking Wildfire hazard mitigation and response capacity Implementing “green” building codes Adjusting timing, size, and location of commercial rafting trips Expanding attractions for tourists during early winter and shoulder season Top on the list of stakeholder concerns was water supply. Specific concerns included worry about potential droughts; decreases in precipitation; and increased calls for water locally, in the arid west, and through Front Range diversions. In addition to concerns about water availability, current water laws were viewed as inadequate to address future pressures to the supply, which stem from the combined pressures of population growth and climate change. Concern over future water availability was mentioned by 10 of 11 stakeholders, many of whom used markedly negative words like “water fights” or “water wars.” As an interesting point of comparison, water was also identified at the 2005 town hall meetings during the development phase of the 2006 Study as the most critical factor related to climate change for the valley. “One of the things that really scares me right now is that the state has at least The next most common vulnerability cited by 600,000 acres feet of a [water] gap that stakeholders was population growth at a local, they figure [means] we won’t have state, regional, and global level. Population was enough water with population growth.” mentioned by 8 of 11 stakeholders, with reasons for concern varying from increased pressure on limited resources to local expansion of development and heavier recreation influence on wildlife areas, increased demand for energy, or greater opportunity for the spread of disease. The third most cited vulnerability was increased wildfire risk from increasing temperatures, drier conditions, and an expanding urban-wildlife interface. 90 Ac`ons  underway   Stakeholders were asked about actions they are already undertaking in response to changes in climate, if any. In the responses, activities that were mentioned typically involved responses that addressed other vulnerabilities as well. For example, the Watershed Action Plan (2012), a collaborative watershed-scale strategy that many interviewees participate in, includes climate change as one of many issues of concern in riparian health and management.118 “What we’ve learned is that it’s beneficial Desired  future  ac`ons     to go slow to go fast. Spend a lot of time with the public engagement and input up front, and then it makes implementation a lot smoother and more efficient.” Even across diverse perceptions of which vulnerabilities are most important, common themes emerged in the type of actions stakeholders recommended. Most frequent was a desire for early planning and discussion that begins before conflicts emerge, particularly in relation to water and fire concerns. Multiple stakeholders also mentioned the importance of long-term monitoring and public outreach. In addition to describing the types of actions they believe are necessary to help meet changes associated with an altered climate, stakeholders also described current actions that they believe to be beneficial. Actions or changes mentioned by at least two different stakeholders included: increased public awareness of the issues, Box 5.3 Desired future actions identified greater local production of food, upgrades to fire fighting infrastructure, movement toward by stakeholders: leave-in-stream water usage rights, • Public education community outreach, and creating • Flexibility in planning and action collaboration among multiple groups and • Crisis plans organizations. • Water conservation planning • Reconsideration of current water laws Constraints   • Local food production • Building codes in relation to fire protection and energy use When asked about barriers to desired and • Long term monitoring current actions, the three top answers were cost, politics, and public awareness, followed by the challenge of addressing water allocation conflicts using current water laws. Other constraints described included: lack of public awareness or interest, technical limitations, concern over industry sway in law-making, and the http://www.roaringfork.org/sitepages/pid362.php for access to the Roaring Fork Watershed Plan and climate related actions. 118 91 need to promote issues in a way that does not make onesided good or bad value statements about the issues or “How do you know? You don’t. And different points of view involved. yet, you’re foolish to go into the future with your eyes closed.” Several other indirect constraints to resiliency planning were common to many of the stakeholders interviewed. One of these constraints was the uncertainty associated with climate projections. As one interviewee put it, “I hate planning for things that I really don’t know are going to happen, and that’s what’s difficult right now.” Several stakeholders cited conflicting or changing results in model projections for the region as contributing to their uncertainty about what future changes to expect. Another barrier to resiliency planning that emerged during the interviews was a mismatch between many stakeholders’ typical planning horizon and the planning horizon of climate models. For stakeholders in governmental roles or connected with water supply issues, some planning consisted of timescales up to fifty years in the future, but for many stakeholders, particularly in the private sector, planning horizons were as short as daily and typically were no longer than 10 years. Discussion about climate change impacts 20 or more years in the future are not immediately relevant to the decision-making time horizon of many individuals, local groups, and businesses. Conclusions Box 5.4 Timescales for planning described by stakeholders. • • • • • “99% of the time I was thinking about the next 20 minutes! There was no 5-year strategy plan.”   “Most of the time it is immediate stress or duress [ of] large capital investments… [we have] a three-year strategic plan.” “When we do our annual goal setting process…they’re usually talking long term, which could be 5, 10, or multidecade type of issues.” “… we try and anticipate what projects we think we need to complete in 10 year increments.”   “In the water work that I do, I am not thinking in particular of a period of years, but I would say long term. A lot of the water clients have to think out 50 years, water supply for 50 years.” On a rating scale of 1-10, with 10 being the most concerned, stakeholder concern about climate change ranged everywhere from a 4 to a 10. The longer the time frame discussed, the greater the concern, particularly for stakeholders who have children. The types of concerns described and the context of the concerns for stakeholders often overflowed the bounds of ecological changes, highlighting an important consideration in adaptation planning: the changes that will occur as a result of climate change will not happen in a static environment. These changes will interact with and be influenced by the political, social, and population dynamics of the future. Plans for climate adaptation therefore must take these parameters, particularly the likelihood of population growth, into serious consideration. 92 CHAPTER  6:  PRELIMINARY  GUIDANCE  FOR   RESILIENCY  PLANNING     Box 6.1 Resiliency planning key points • • • • • A variety of motivations drive individuals and groups to engage in resiliency planning and implementation Planning to increase resiliency requires an iterative, collaborative, and ongoing process Multiple pathways exist to reduce risk and enhance resiliency Considering multiple criteria when defining goals and objectives is possible Continuous stakeholder engagement and involvement is a critical component As stated in the introduction to this report, the purpose of this study is to inform the City in its pursuit of climate resiliency planning. In this section we provide preliminary guidance for resiliency planning efforts, which are intended to support adaptation to climate risks by individuals, groups, and the community-at-large across sectors. Mo`va`ons  for  resiliency   planning   Society at different levels of organization, from individuals to businesses and from cities to nations, will almost certainly face some climate-related changes. These encounters may be realized as either costs or benefits, depending on the nature of change, vulnerability, and exposure, as well as response capacity. Motivations to engage in resiliency planning will vary given the heterogeneous nature of impacts and ability or willingness to consider scenarios of change in future planning and decisionmaking. In addition, different elements of society have various responsibilities to uphold, whether they be obligations to constituents, rate payers, shareholders, owners, family members, or neighbors. Awareness of the range of actual or potential motivations enables those who 93 spearhead resiliency planning within a community to facilitate a more inclusive, robust, and transparent planning process. Examples of motivations: • Municipal and regional government motivations Providing for long-term health, safety, and well-being of the community Continuity of essential services (e.g. utilities, emergency response) Supporting economic and cultural growth of the community Avoiding costly damages from climate-related events • Business and non-profit motivations Maintaining the continuity of operations and missions Avoiding costly damages from climate-related events Identifying and exploiting new opportunities • Individual motivations Preservation of community, local values, and culture Avoiding costly damages from climate-related events Participating in and contributing to civic process Civic ownership in working toward a healthy, resilient and sustainable community • • • • • • • • • • • Adapta`on  planning  process   Figure 1.1, presented in Chapter 1, depicts adaptation as one component of local resiliency capacity. Figure 6.1 further describes the process of adaptation planning and illustrates it as an iterative, ongoing cycle. As progress is made in building resiliency, this process is renewed with another cycle of assessment, action, and evaluation. While this idealized and simplified model does not necessarily capture the exact order or all component parts of adaptation in actual practice, the essential point is that adaptation is a continuous process of learning, planning, implementing, and evaluating. One key attribute of this process is that to be successful it goes beyond a planning process into the realization of changes to policies, operational procedures, infrastructure, and the fabric and awareness of the community. The component parts of Figure 6.1 are: • Learning & Assessment: Preparing to adapt begins with understanding local context and identifying risks pertinent to that locality. This involves an integrated assessment of physical, ecological, and societal impacts both currently and in the future and the ability to incorporate new information about impacts and adaptation options over time. 94 • Planning & Engagement: Armed with the best-available relevant information and understanding of the profile of risks pertinent to the community, individuals and groups begin developing strategies to reduce impacts or exploit beneficial opportunities. This involves setting measurable goals. It also involves engagement of stakeholders who may be helpful in implementing these strategies as well as those groups that may be impacted, either positively or negatively, by the consequence of anticipated actions. • Implementation & Monitoring: Implementation of proposed response strategies also incorporates a monitoring component to provide the data essential to analysis of performance measured against the established goals. • Evaluation: The final stage identifies areas for improved process and implementation and charts the course for embedding learning before the initial “trip around the wheel” begins anew (see “Criteria for Success” below). To make the process truly a cycle, the process begins again at step one with additional learning assessment and carries on through completion of the cycle. An example of this idealized process in action can be found in Keene, New Hampshire’s Climate Resilient Communities Adaptation Planning Process which includes five milestones:119 • • • • • Conduct a climate resiliency study Prioritize areas for action and set goals Develop an adaptation action plan Implement the action plan Monitor, evaluate, and update the plan Types of response Adaptation involves a suite of actions undertaken by individuals, groups, and governments, both autonomously and in response to policy. It is important to recognize that there are multiple types of responses to consider when formulating response strategies. While the exact set of responses will vary depending on the risks confronted and the options available, consideration of the full range of options allows individuals and the community as a whole to strategically invest in and pursue actions that most effectively mitigate risk while also maximizing opportunities or aligning with co-benefits. It is important to note that adaptation measures are City  of  Keene  New  Hampshire  and  ICLEI.  2007.  Adapting  to  Climate  Change :  Planning  a  Climate  Resilient   Community  November  2007.  Keene,  New  Hampshire. 119 95 often, if not always, implemented in response to multiple rationales, not just climate change alone.120 Table 6.1 illustrates that a variety of responses can be used to address a single issue. It presents six categories of response with potential examples for wildfire risk reduction. The responses are intended to serve as examples only and not as recommendations. Figure 6.1 Adaptation planning for climate risk reduction I. Learning & Assessment! IV. Evaluation! Adaptation Planning Cycle! III. Implementation & Monitoring! II. Planning & Engagement! Figure 6.1 Planning in the context of change is often best supported by an adaptive planning process that is cyclical rather than linear and allows for learning and adjustment along the way. Initial learning and assessment (I) informs planning and initial engagement with the community (II). Plans are then implemented and long-term monitoring based on goals and objectives (III) enable evaluation. As learning takes place within the sectors of our community — what worked, what didn’t and why — the adaptive management cycle begins anew building both goals of resiliency and sustainability. Criteria for success This chapter has stated that resiliency planning requires ongoing iteration based on ongoing learning, monitoring, evaluation, and adjustment to new information. While this is important, it 120  Adger  et  al.  2007. 96 begs the question, what is an ideal future state to plan toward, and by what criteria is success measured? Successful adaptation to climate change that enhances preparedness and promotes resiliency cannot be measured entirely by quantitative benchmarks, nor can it be evaluated by one dimension alone. The following are criteria to consider, based upon descriptions of “successful adaptation” developed by researchers Susanne Moser and Maxwell Boykoff:121 Table 6.1 Categories of response for climate change risk reduction Categories of response Examples of actions with fire as case study Reduce exposure Relocating high value assets from at-risk areas; adjusting timing of activities during periods of potential impact Response and recovery preparedness Improving capacity of emergency responders and reducing recovery time between events Increase resilience to changing risks Ensuring continuity of critical services during and after event; post-event communication strategies for community and tourists Reduce vulnerabilities Developing resources that harden infrastructure and services to extreme events Transfer and share risks Transformation Promoting collaborative planning and action with stakeholders and neighboring governments Creating an integrated approach to mitigate underlying cause of risk while also coordinating resiliency enhancement and vulnerability reduction Adapted from Moser & Boykoff, 2013 • Economic protection – minimizing or avoiding losses from climate-related damages, while at the same time capitalizing on potential financial benefits 121  Adapted  from  Moser  and  Boykoff  2013. 97 • Institutional and policy adequacy and legitimacy – preserving the ability of institutions and policies to meet obligations to residents/constituents as well as non-human systems (e.g. ecosystems) • Ecological and environmental protection – preserving the resiliency capacity, diversity, and services made possible by health ecosystems and broader environmental conditions • Social justice – reducing vulnerabilities and/or inequities within marginalized populations while strengthening communities and the well-being of all members
 • • Political and procedural integrity – supporting transparent and inclusive processes Cultural and psychological factors – preserving and/or enhancing vital aspects of community (e.g. the “Aspen idea”) Lessons  from  other  communi`es   Table 6.2 compiles four examples of other communities—ranging from small to large—that have made steps (of varying length) towards climate resiliency planning. Table 6.2 Selected examples of climate adaptation plans Place Date Title Helpful Feature 2007 Adapting to Climate Change : Planning a Climate Resilient Community Outlines idealized Click here. framework for planning Boulder, CO 2012 Boulder County Climate Change Preparedness Plan Allows for integration of guidance into existing departmental structure Click here. Moab, UT 2010 Forest and Water Climate Adaptation Clearly defines goals, actions, and responsible parties Click here. King County, WA Climate Plan (2007); Strategic Climate Action Plan: What King County is Doing 2007, 2012 to Reduce GHG Emissions and Prepare for the Impacts of Climate Change (2012) Integrates approaches for adaptation and mitigation and aims to be a leader in the field of climate planning. Also, contains update to see evolving structure. 2007: Click here. 2012: Click here. Keene, NH Link 98 More plans and resources from other communities may be searched through: Georgetown Climate Center: State and Local Adaptation Plans http://www.georgetownclimate.org/adaptation/state-and-local-plans • • • Climate Adaptation Knowledge Exchange (CAKEX) http://www.cakex.org • Stakeholder  engagement   Chapter 5 presents input and ideas gleaned from an early round of stakeholder interactions conducted for the purposes of this study. These stakeholder interviews represent just one of many techniques for eliciting stakeholder participation, and multiple strategies will likely need to be pursued to capture the diversity of stakeholders and perspectives that exist. Examples of forums and mechanisms for gathering stakeholder input may include: • • • • • • In-depth stakeholder interviews Town hall meetings Public input forums Visitor/resident surveys Collaborative planning workshops and meetings Public outreach and education on key topics
 99 CHAPTER  7:  CONCLUSION   The observations, projections, and research presented here—as well as in other reports ranging from other local studies to international assessments—convey increasing confidence about climate change and its significant consequences for society and ecosystems. Taken together, this evidence impels communities large and small to think about preparations that build resiliency. Aspen has the opportunity to lead in this arena, particularly among mountain resort communities, though it is likely that Aspen’s efforts will move forward alongside many other communities considering similar actions. Mutual learning among communities is therefore likely to occur and may be a vital component in meeting objectives under an increasingly urgent timeline. While uncertainty remains in many areas important to decision-making, there is now enough information to characterize a range of possible futures. Uncertainty may appear at first to be a barrier to action, but utilization of multiple scenarios and accommodating multiple future outcomes in planning and implementation has the potential to strengthen the overall security and sustainability of a community. This report is a basis for future planning at the City of Aspen and the surrounding community. Any one of the issues raised in this study could be examined in more depth, either through exploring references included within the report or through additional research. It is likely that for some of the potential impacts, significantly more site-specific study and research is needed. As one example, evaluating changing risks from fire, flood, landslide, or drought requires detailed examination of local risk conditions and evaluation of existing response capacity and resilience. Only from such a specific basis of information could specific response strategies be adopted. 100 It is also recommended that careful attention be focused on stakeholder communication and engagement. A diversity of views, interests, and local expertise exists in the community and incorporating that breadth of knowledge into resiliency planning is likely to ensure more success during implementation. Moving forward, there are several areas of research and resource development that could continue to support the resiliency planning process as it moves forward: 1. Assessment of potential economic gains and losses resulting from projected impacts. An early effort to look into the financial ramifications of climate change was conducted for the 2006 Study, but the findings were only very general. Analysis of economic drivers and their seasonal vulnerabilities in the context of climate change could inform fiscal planning and also serve as a basis to justify future investments in both mitigation of and adaptation to climate change. 2. Development or adaption of interactive tools that support local decision-making. Decision support tools, such as systems models or game strategies that consider possible scenarios, can help illustrate the interlinking effects of climate change and proposed responses in particular sectors of interest. Tools developed from other regions may be adaptable to the Aspen area as well as new resources developed specifically for Aspen. 3. Wider assessment of climate-related impacts to the Roaring Fork Valley and opportunities for collaborative planning and implementation. Climate impacts to Aspen will not happen in isolation from impacts felt throughout the Valley and surrounding region. Identifying areas where impacts beyond the Aspen community are similar to those likely to be experienced in Aspen could offer one extension of this study. Another area for further investigation could be impacts external to Aspen that may have local impacts. Collaboration with other communities within the Roaring Fork Valley may enable this type of work. These types of activities could complement other efforts pursued by the City, such as engaging with networks of other communities pursuing resiliency planning, the Western Adaptation Alliance being one example. Over time, it is possible that adaptively managing for climate change will become a commonplace activity pursued routinely at the municipal level and integrated into many current departments. Although much change is anticipated as a result of climate change in the coming years and decades, there is still time for society to address its underlying drivers as well as prepare for its many unavoidable effects. As a mountain resort, Aspen may very well feel the impacts of climate change more quickly and even more severely than other small communities, yet its longstanding leadership and aggressive action on this issue will help it to prepare and build resilience.
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A Report by the U.S. Climate Change Science Program and the Subcommittee on Global Change Research. [Gamble, J.L. (ed.),K.L. Ebi, F.G. Sussman, T.J. Wilbanks, (Authors)]. U.S. Environmental Protection Agency, Washington, DC, USA: 89–109. 108 Appendix  A   Review  of  results  from  2006  Study     In 2005, amid growing interest and concern in the Aspen area about climate change and its potential local impacts, AGCI was engaged by the City to assess climate change impacts and potential responses. The report helped to launch the Canary Initiative and engaged elected officials, citizens, and members of the scientific community. Town Hall meetings and stakeholder interviews revealed a growing concern about climate change and how it would affect water, skiing, summer tourism, agriculture, fire, invasive species, pest risk, and more. Selected key findings from the 2006 Study include: Climate Observations (1980-2004) • • • Average temperatures in Aspen increased 3.0ºF Total precipitation has decreased 6%; snowfall decreased 16% at 10,600 feet; total precipitation decreased 17% Frost free period increased by 20 days Climate Projections • • • • 2030: Average annual temperatures increase 3-4ºF from 1990 with the middle world greenhouse gas emissions scenario (SRES A1B) 2100: Projected temperatures increase as much as 16ºF for high emissions scenario (SRES A1FI) Projected precipitation change less certain; climate models indicate a possible mid-range decrease of 7% by 2030 (SRES A1B) The course of the world’s current future greenhouse gas emissions scenario will significantly influence end-of-century projections for temperature and precipitation Ecosystem Impacts • Rising temperatures may render local coniferous forests vulnerable to insect infestation, especially to bark beetles 109 • • • Changes in climate may contribute to endangerment of “habitat specialists,” such as ptarmigan and pika CO2 fertilization may promote growth in noxious weeds Shift in eco-zones from lower to higher elevations Socioeconomic Impacts & Analysis • • • • • Vulnerabilities of Aspen Skiing Company include under-target snowfall, curtailed ski season, altered perception of snow quality by tourists, and beginner hill degradation Resiliency assets of Aspen Skiing Company include: operations on four mountains, capacity for snowmaking, lift downloading to base, and financial resources Greater uncertainty in residential investments (e.g. 2nd home preferences) Potential to maintain better snow conditions than many competing resorts due to high elevation and relatively colder temperatures Three quarters of all spending in Aspen comes from visitor spending, and three quarters of winter visitor spending is directed toward skiing Hydrology on the Roaring Fork River • • • • 2030 and 2100 projections among all scenarios considered show earlier peak runoff Increased challenges in meeting minimum stream flows Less water stored as snow, more annual precipitation as rain projected for the future. Projected higher temperatures may have greater effect on streamflow than projected minor changes in precipitation (due to snowmelt, sublimation, evaporation, and evapotranspiration) 110 Appendix  B   Methodology  and  addi`onal  results  from  CMIP5  modeling   Methods In the modeling studies included within the 2006 Study, Claudia Tebaldi and Linda Mearns from the National Center for Atmospheric Research utilized a Bayesian statistical technique to synthesize the information contained in an ensemble (collection) of different GCMs, run under historical and future scenarios, into probability distribution functions of projected temperature and precipitation change. In that work, the analysis was performed at a regional scale for four grid boxes surrounding Aspen, as shown in Figure B.1. This method’s results are aimed at representing the expected signal of anthropogenic change (i.e. change Figure B.1 Location of CMIP5 grid cells induced by human sources of greenhouse gases and land use change). The actual climate at the times of these various projection horizons will reflect both the strength of this signal and the natural variability in the climate system that will be superimposed to it. The area represented by the grid boxes was chosen to reflect primarily the Western Slope and Colorado Plateau and the Upper Colorado River Basin. The analysis technique weighted model results based on convergence with other model results in the cohort as well as a bias adjustment for result Figure B.1 shows the region considered in the proximity to observed results during CMIP5 GCM model. Analysis of CMIP5 GCM model the historical base period output was performed at a regional scale for 4 gridpoint surrounding Aspen, covering the area from (1980-1999). The GCMs assessed in 105.50W – 111.06º W and 36.30-41.84º N), as 2006 using this method were the 21 shown approximately above. GCMs (20 for precipitation) conducted as part of the Coupled Model Intercomparison Project 3 (CMIP3), which were assessed in 2007 by the IPCC. Generally the climate models are improving in how well climate models can represent past climates, but how well models represent the past does not equate to how well features of the future climate will be captured. Multi-model ensembles are used in order to help better capture the range of uncertainty that exists when modeling future conditions 111 For this 2014 study, Claudia Tebaldi utilized the same method and grid cells as in 2006 but additionally analyzed results generated from a new generation of climate models. The results presented in this report assess results from 33 GCMs run as part of the Coupled Model Intercomparison Project 5 (CMIP5), which were recently assessed in 2013 by the IPCC.
 Table B.1 Comparison of CMIP3 (2006 Study) to CMIP5 (2014 Study) results 2014%Results%(CMIP5) 2006%Results%(CMIP3) RCP$4.5$Temp$Change$(ºF)$from$1980;1999$Average Time$Period DJF MAM JJA SON 2020;2039 2.7 2.9 2.9 2.8 2050;2069 4.5 4.4 4.6 4.3 2080;2099 5.2 5.3 5.4 5.3 B1$Temperature$Change$from$1980;1999$Average Time$Period DJF MAM JJA SON 2000;2020 1.4 1.1 1.4 1.3 2040;2060 2.9 2.9 3.6 2.9 2080;2100 4.7 4.3 5.4 4.5 RCP$6.0$Temp$Change$from$1980;1999$Average Time$Period DJF MAM JJA SON 2020;2039 2.0 2.6 2.5 2.2 2050;2069 4.0 4.5 4.4 4.2 2080;2099 6.6 6.8 6.3 6.6 A1B$Temperature$Change$(ºF)$from$1980;1999$Average Time$Period DJF MAM JJA SON 2000;2020 1.1 1.1 1.4 1.3 2040;2060 3.8 4.1 5.2 4.3 2080;2100 6.5 6.5 8.1 6.8 RCP$8.5$Temp$Change$(ºF)$from$1980;1999$Average Time$Period DJF MAM JJA SON 2020;2039 2.8 2.9 3.1 2.9 2050;2069 6.0 5.9 6.5 6.3 2080;2099 9.3 9.1 10.5 10.1 A2$Temp$Change$from$1980;1999$Average Time$Period DJF MAM JJA 2000;2020 1.1 1.1 1.4 2040;2060 3.6 3.8 4.9 2080;2100 7.4 8.1 9.9 SON 1.4 4 8.5 RCP$4.5$Precip$Change$(%$of$1980;1999$average) Time$Period DJF MAM JJA SON 2020;2039 4.8 ;1.1 0.8 1.3 2050;2069 4.6 1.3 1.6 2.1 2080;2099 6.4 1.1 2.4 2.3 B1$Precip$Change Time$Period DJF 2000;2020 4.5 2040;2060 3.9 2080;2100 5.9 SON ;0.1 2.6 0.6 RCP$6.0$Precip$Change$(%$of$1980;1999$average) Time$Period DJF MAM JJA SON 2020;2039 1.9 2.2 ;2.6 1.0 2050;2069 4.1 3.7 1.0 ;2.0 2080;2099 5.7 5.6 6.2 3.9 A1B$Precipitation$Change$(%$of$1980;1999$average) Time$Period DJF MAM JJA SON 2000;2020 2.5 ;1.9 ;4.1 ;0.7 2040;2060 6.7 ;4.7 ;8.2 0.6 2080;2100 10.4 ;7.5 ;10.7 ;0.5 RCP$8.5$Precip$Change$(%$of$1980;1999$average) Time$Period DJF MAM JJA SON 2020;2039 5.1 0.5 0.9 1.3 2050;2069 8.6 1.1 1.4 0.8 2080;2099 14.0 ;0.1 0.8 1.9 A1FI$Precipitation$Change Time$Period DJF MAM 2000;2020 4.0 ;0.7 2040;2060 9.3 ;6.1 2080;2100 11.8 ;15.7 MAM ;0.9 ;1.4 ;2.2 JJA ;4.8 ;5.5 ;4.5 JJA ;7.6 ;7.4 ;8.4 SON 0.0 2.1 6.3 Table B.1 2006 results were included in the AGCI 2006 Study and were provided by Tebaldi and Mearns. 2014 results reported on in this study utilized the same methodology (Tebaldi and Mearns, 2007) and were provided by Tebaldi. 2014 results utilize RCP emissions scenarios, similar but not identical to SRES scenarios utilized in 2006. Results are presented by three month groupings approximating the four season timeframes: DJF is December, January, February; MAM is May, April, May; JJA is June, July, August; SON is September, October, November. For precipitation, green highlighting indicates projected increases and red highlighting indicates projected decreases. On balance, 2014 results based on CMIP5 models indicate more positive precipitation results than 2005 results based on CMIP3. 112 Figure B.2. Projected temperature change in Western Colorado region by 2030 and 2090 (see caption after B.3) 113 Figure B2. Projected precipitation change in Western Colorado region by 2030 and 2090 by season 114 Caption to Figure B.2 : Figure B.2. shows probability distribution functions (PDFs) of projected temperature change for Western Slope region by future periods, seasons, and scenarios. Color coding indicates three emissions scenarios considered—RCP 4.5 (blue), a low emissions scenario comparable to B1 utilized in 2006; RCP 6.0 (green), a medium emissions scenario comparable to A1B used in 2006; and RCP 8.5 (red), a high emissions scenario comparable to A2 used in 2006. Results are presented by three month groupings approximating the four season timeframes: DJF is December, January, February; MAM is May, April, May; JJA is June, July, August; SON is September, October, November. Temperatures presented are in degrees Celsius difference between historical conditions observed 1980-1999. Caption to Figure B.3: Figure B.3 shows probability distribution functions (PDFs) of projected precipitation change for Western Colorado region. Color coding indicates three emissions scenarios considered—RCP 4.5 (blue), a low emissions scenario comparable to B1 utilized in 2006; RCP 6.0 (green), a medium emissions scenario comparable to A1B used in 2006; and RCP 8.5 (red), a high emissions scenario comparable to A2 used in 2006. Results are presented by three month groupings approximating the four season timeframes: DJF is December, January, February; MAM is May, April, May; JJA is June, July, August; SON is September, October, November.. Precipitation is represented as a percentage change from average conditions 1980-1999. 115