National Aeronautics and Space Administration Headquarters Washington, DC 20546-0001 May 31, 2019 Reply to attn. of: Office of Communications Mr. Benjamin Levitan and Lance Bowman Environmental Defense Fund 1875 Connecticut Ave., NW Suite 600 Washington, DC 20009 Re: FOIA Tracking Number 19-HQ-F-00404 Dear Mr. Levitan and Bowman: This is the final response to your Freedom of Information Act (FOIA) request to the National Aeronautics and Space Administration (NASA), dated March 25, 2019, and received in this office on March 26, 2019. You sought numerous records pertaining to any climate review. In an email dated April 1, 2019, however, you clarified that your request seeks records pertaining to a meeting reportedly convened by the White House/National Security Council in February 2019 regarding a review of climate science. Specifically, you seek records pertaining to: 1) Any invitation or request for NASA to participate in the February 2019 meeting, or any other meetings concerning climate science; 2) Whether NASA participated in any meetings or discussion related to climate science; 3) Any discussions about the nature and extent of NASA’s involvement in climate science; and 4) Anything else about the White House/National Security Council review of climate science, such as its structure, goals, purpose, and methods. Our interim response, dated May 8, 2019, summarized our work on your request thus far. It also provided you with 57 pages of records obtained from our search within ITCD, and advised that we would provide you with another response once our review of records located in the Office of Interagency and Intergovernmental Relations (OIIR) is complete. That review is now complete and remaining records from ITCD as well as OIIR are enclosed. Please note that the enclosed records include communications originating from the National Security Council (NSC), a component of the White House that is not subject to the FOIA. Although these communications from the White House do not constitute “agency records” that are subject to FOIA, NASA consulted with the NSC in an effort to release to you as much information as possible. Thus we, in consultation with the NSC, reviewed under the FOIA the responsive records to determine whether they may be accessed under the FOIA's provisions. Based on that review, this office is providing the following: 2 50 page(s) are being released in full (RIF); 10 page(s) are being released in part (RIP); 10 page(s) identified as non-agency records per consultation with National Security Council; NASA redacted from the enclosed documents certain information pursuant to the following FOIA exemptions: Exemption 6, 5 U.S.C. § 552(b)(6) Exemption 6 allows withholding of “personnel and medical files and similar files the disclosure of which would constitute a clearly unwarranted invasion of personal privacy.” 5 U.S.C. § 552(b)(6)(emphasis added). NASA invokes exemption 6 to protect the names of private individuals, as well as email addresses and other contact information of third parties referenced in these records. Appeal You have the right to appeal my action on your request. Please send any appeal to: Administrator NASA Headquarters Executive Secretariat ATTN: FOIA Appeals MS 9R17 300 E Street S.W. Washington, DC 2054 Both the envelope and letter of appeal should be clearly marked, “Appeal under the Freedom of Information Act.” You must also include a copy of your initial request, the adverse determination, and any other correspondence with the FOIA office. In order to expedite the appellate process and ensure full consideration of your appeal, your appeal should contain a brief statement of the reasons you believe this initial determination should be reversed. Assistance and Dispute Resolution Services For further assistance and to discuss any aspect of your request you may contact NASA’s Principal FOIA Officer, Nikki Gramian, via telephone at 202-358-0625 or via e-mail at Nikki.N.Gramian@NASA.gov. You may also send correspondence to Ms. Gramian at the following address: Freedom of Information Act Office National Aeronautics and Space Administration NASA Headquarters 300 E Street, S.W., 5P32 Washington D.C. 20546 Fax: 202-358-4332 3 Additionally, you may contact the Office of Government Information Services (OGIS) at the National Archives and Records Administration to inquire about the FOIA mediation services it offers. The contact information for OGIS is as follows: Office of Government Information Services National Archives and Records Administration 8601 Adelphi Road-OGIS College Park, Maryland 20740-6001 Email: ogis@nara.gov Telephone: 202-741-5770 Toll free: 1-877-684-6448 Fax: 202-741-5769 Important: Please note that contacting any agency official including the undersigned, NASA’s Principal FOIA Officer, and/or OGIS is not an alternative to filing an administrative appeal and does not stop the 90 day appeal clock. Sincerely, Electronic signature /S/ Stephanie K. Fox Team Lead / Chief FOIA Public Liaison Enclosures Re: Daily on Energy, presented by GAIN: Rift grows in GOP over climate change ... Greens celebrate Endangered Species Day From: To: Cc: Sent: Received: Thomas Wysmuller <(b)(6) William Happer Bridenstine James , Singer S. Fred , Bridenstine, James F. (HQ-AA000) May 19, 2018 11:12:32 AM EDT May 19, 2018 11:12:44 AM EDT Hi, Wil: I’ll embed my reaction within your e-mail On May 19, 2018, at 8:27 AM, William Happer b6 wrote: Dear Tom, Thanks for the assessment. With repect to Fred Singer's WSJ Op Ed, I was surprised to read what seemed to be a statement that the rate of sea level rise is "accelerating." I don’t see that in the tide gauge data. Neither do I. Could this be another editorial improvement? Quite likely. Fred told me he is limited to typing with only one hand, and was having a difficult time doing so. I asked him to send me the final WSJ submission (that I was originally supposed to get prior to its delivery), and he thinks it may have been accidentally erased. Some of the “factoids” that I talked to Fred about ended up in his thinking, but the floating Ross Ice Shelf contributing to SLR was not one of them. He did use some of the Zwally paper’s conclusions, but reference to it was either omitted or deleted by the WSJ. And how Bridenstein or anyone else can say that humans are a major cause of warming is a puzzle to me. I’ll go along with humans playing a major role in the increase of CO2 in the atmosphere, from a relatively steady 280ppm for the past two thousand years +, to over 400ppm, starting in the late 1700s, but oceanic warming did not follow at anything near the CO2 increase rate. Whatever warming we have had over the past 50 or so years is indistinguishable from many previous warmings. You are absolutely correct!!! Per EPICA and Vostok, the past three interglacials each were warmer than the present, and there were no factory or transportation emissions helping boost temperatures along back then. I still believe Jim Bridenstine was trying to diffuse what is essentially a non mission-critical issue, as the Potomac estuary will not inundate NASA Headquarters anytime soon, or within anyone’s lifetime either. NASA is an agency far different than the one I worked in during the Apollo days, and the challenge Jim faces will be getting it back to a nononsense, measured and validated data orientation. Catastrophic SLR and runaway temperature rise is part of the nonsense, and he will be wise to systematically sidestep it for the short term. Tom Will _____ From: Thomas Wysmuller (b)(6) He’s entered a hornets nest without a smoke pot and I hope will methodically let the NASA “hive” settle down. There is much to do there, major mission critical work in fact, and having a climate oriented disruption during his first month is not in his, or the nation’s, best interest. My guess is that he intelligently quickly read the “lay of the land” and is acting accordingly. I do intend to eventually see Jim Bridenstine at some time in the next month or so, but well after the NY climate conference where I’ll be with b6 next week. On another issue, Fred Singer was going to collaborate with me on an article he was putting together for the WSJ, but for some reason went at it on his own. According to a phone conversation I had with Fred earlier tonight, the WSJ severely edited it, and the usual suspects are jumping all over it, to Fred’s dismay. Best to you, Wil, and I hope you don’t mind the ccs! Tom PS No bccs On May 18, 2018, at 11:05 PM, William Happer b6 > wrote: Dear Tom, Do you have any insight about the remarks attributed to Bridenstine below? Will Begin forwarded message: From: Washington Examiner > Subject: Daily on Energy, presented by GAIN: Rift grows in GOP over climate change ... Greens celebrate Endangered Species Day Date: May 18, 2018 at 12:39:42 PM PDT To: b6 @rangemagazine.com > Reply-To: Washington Examiner > Washington Examiner's Daily On Energy Newsletter View this as website Doc 8 Re_ Daily on Energy, presented by GAIN_ Rift grows in GOP over climate dod SHARE: Share on Facebook Share on Twitter Share on Google+ ADVERTISEMENT SIGN UP! If you’d like to continue receiving Washington Examiner's Daily onEnergy newsletter, SUBSCRIBE HERE: http://newsletters.washingtonexaminer.com/newsletter/ daily-on-energy/ RIFT GROWS IN GOP OVER CLIMATE CHANGE: Republicans who support combating climate change were shaking their heads Friday after a “wild day” during which members of the GOP expressed divergent views on the subject. “Thursday was a wild day that shows us that most GOP representatives’ views on climate science are informed more by their ideological commitments than empirical fact or careful study,” Joseph Majkut, director of climate policy at the Niskanen Center, a free-market think tank, told Josh. Rock and a hard place: Early Thursday, Rep. Mo Brooks, R-Ala., said that rocks falling into the ocean are causing sea levels to rise, preaching climate denial during a hearing focused on technologies that can help address global warming. Brooks, a Tea Party Republican, said rocks from the California coastline and the White Cliffs of Dover tumble into the sea every year, contributing to sea-level rise. "Every time you have that soil or rock or whatever it is that is deposited into the seas, that forces the sea levels to rise, because now you have less space in those oceans, because the bottom is moving up," Brooks said from his perch on the Science, Space and Technology Committee. Steve Valk, director of communications of the Citizens’ Climate Lobby, a group focused on inspiring Republicans to take climate action, called Brooks’ remark the “hand-slapping-forehead moment of the week.” ‘Put politics aside’: Later in the day, Rep. Carlos Curbelo, R-Fla, a moderate whose state is already feeling the effects of sea level rise, boasted in an enthusiastic press release that the Climate Solutions Caucus that he heads had added five new members, including three Republicans. The new GOP entrants, Reps. Erik Paulsen of Minnesota, Peter Roskam of Illinois, and Tom MacArthur of New Doc 8 Re_ Daily on Energy, presented by GAIN_ Rift grows in GOP over climate Jersey, bring the climate caucus membership to 78, half of whom are Republicans, showing that Congress can “put politics aside” to combat climate change, Curbelo said. ‘Major way’: But politics surely affected the calculus of former House conservative lawmaker Jim Bridenstine of Oklahoma, who expressed denial of humans’ role in climate change before becoming the new administrator of NASA last month. Now that he heads an agency that studies the changing climate, and doesn’t represent a conservative district in Congress, Bridenstine is expressing new views. "I fully believe and know that the climate is changing. I also know that we, human beings, are contributing to it in a major way," Bridenstine told NASA employees at a town hall-style meeting Thursday. Majkut and Valk hope the actions of Bridenstine and the Climate Solutions Caucus’ Republicans send a message to other conservatives. Patience please: “Low information beliefs are malleable,” Majkut said. “Look what happened with Mr. Bridenstine. As soon as he started working with a bunch of experts down the hall, his rhetoric shifted substantially. I hope his leadership demonstrates that one can fully embrace climate science, or even think climate change is bad, without surrendering his membership in the Conservative movement.” Added Valk: “Progress is being made. Patience will eventually be rewarded.” This email was sent tob6 rangemagazine.com manage.com/about?u=00b18e7544dd3ec267591c592&id=3b3366c1c8&e=3264bae676&c=8680e5cb0c> why did I get this? unsubscribe from this list update subscription preferences MediaDC · 1152 15th St NW Ste 200 · Suite 200 · Washington, DC 20005-1799 · USA Doc 8 Re_ Daily on Energy, presented by GAIN_ Rift grows in GOP over climate FW: NASA website From: To: Sent: Received: Happer, William EOP/NSC February 26, 2019 9:53:18 AM EST February 26, 2019 9:53:21 AM EST > Dear James, Not an Agency Record thanks for the kind greeting from Jim Bridenstine. Not an Agency Record Best wishes, Will -Dr. William Happer Deputy Assistant to the President Senior Director for Emerging Technologies Doc 9 FW_ NASA website National Security Council b6 From: William Happer > Subject: [EXTERNAL] Fw: NASA website From: b6 Sent: Tuesday, February 26, 2019 3:57 AM To: William Happer Cc: b6 Subject: NASA website 26th February 2019 Dear Will It's been a while since we last communicated and I'm contacting you with reference to the NASA website and its climate content for kids at: >https://climatekids.nasa.gov/menu/weather-and-climate/< <>https:/climatekids.nasa.gov/menu/weather-and-climate/<> And the main NASA climate site at: >https://climate.nasa.gov/evidence/< <>https:/climate.nasa.gov/evidence/<> In Australia, many primary school teachers (and secondary) use the NASA website to teach about climate change and most have very little science background so essentially the blind are leading the blind, trusting the accuracy of information on climate provided by NASA. Much of the material on both sites are biased, emotive and without any evidence. There are statements such as: "Ninety-seven percent of climate scientists agree that climate-warming trends over the past century are very likely due to human activities, and most of the leading scientific organizations worldwide have issued public statements endorsing this position." And: "The Maldives are vulnerable to sea level rise." The site references the IPCC and Ben Santer as authorities, ignoring many facts that oppose the alarmism. I'm concerned that many children are being indoctrinated by this bad science. I have emailed the Site Editor Holly Shaftel and Site Manager Randal Jackson putting forward my constructive criticism with evidence but received no reply. I have mailed a letter (yes - one with stamps!) to the NASA administration and received no reply. Are you able to give me any email addresses for personnel at NASA who might do something about this misinformation that a trusting public will accept without question. Many thanks and kind regards. Doc 9 FW_ NASA website b6 b6 P.S. I hope global warming isn't bringing too much snow to your area. Doc 9 FW_ NASA website Re: Feedback? Thomas Wysmuller <(b)(6) b6 Doiron Hal wrote: Tom, Thanks a lot for dropping your dime on Will’s desk! “By chance, Tom Wysmuller stopped by my office on Saturday,…” I love it! You never cease to amaze me. b6 From: Hal Doiron [mailto b6 ] Sent: 4 March, 2019 12:23 PM To: b6 Cc b6 ; b6 , FYI. I took my shot at getting involved with the Trump Administration's review of climate science that Dr. Will Happer is heading up in his role as New Technology Adviser to John Bolton, the National Security Advisor. Tom Wysmuller, Thanks for suggesting Will Happer send me his paper for review. What have you learned about how he plans to conduct the internal Administration review of the Anthropogenic Global Warming (AGW) threat? Hal Harold H. Doiron, PhD b6 Home/Ofc: b6 Doc 10 Cell: b6 Re_ Feedback_ ----- Forwarded Message ----From: Hal Doiron > Cc: b6 b6 b6 > b6 Sent: Monday, March 4, 2019 12:15:59 PM CST Subject: Re: Feedback? >> > >; > Will, I am honored that you would want me to review your paper. I will get to it this week. I am also very eager to get involved with the internal government review of climate science that newspaper reports indicate you are organizing. As you know, I have been leading a NASA retiree independent assessment of the Anthropogenic Global Warming (AGW) issue for the last 7 years. Our assessment of GHG climate sensitivity is completed and we believe Transient Cilmate Response is bounded to the high side by 1.3C and Equilibrium Climate Sensitivity is <1.6C. Our results are essentially the same as published by Lewis and Curry (2018) using similar data. We derived a simple algebraic global mean surface temperature model from Conservation of Energy (Power in W/m^2) considerations and validated it with HadCRUT4 global temp data and AR5 atmospheric GHG and aerosol concentration history since 1850. Our analysis assumed the generally accepted reduction in IR flux leaving the atmosphere for doubling CO2 concentration was 3.71 W/m^2, and that surface temperature would adjust to compensate. We conservatively assumed that all observed HadCRUT4 global surface temperature increase since 1850 was due to rising atmospheric GHG and aerosol concentrations and none was due to a likely natural 1000 year warming cycle that fits the Roman Warm Period, Medieval Warm Period AND Little ice Age surface temperature variations, and that should peak out in about 2100. The HadCRUT4 data and atmospheric GHG history allowed us to determine Transient Climate Response which was an undetermined constant in our simple algebraic model that related surface temperature to atmospheric GHG concentration. Our value for Transient Climate Response is < 1.3C including all climate feedbacks. The generally accepted 1.1C warming value for surface temperature increase without climate feedbacks due to doubling CO2 concentration (ie. due only to the 3.71 W/m^2 reduction in outgoing IR flux). This proves with data that climate feedbacks have at most, a small positive effect. When natural warming cycle effects in the temperature data are considered, climate feedbacks could be negative, or stabilizing. At any rate, there is no cause for climate alarm and we estimate <1C additional warming by 2100 (should be beneficial) due to burning all currently known world-wide reserves of coal, oil and natural gas. Best regards, Hal Doiron Sent from Yahoo Mail on Android &c=Global_Internal_YGrowth_AndroidEmailSig__AndroidUsers&af_wl=ym&af_sub1=Internal&af_sub2=Global_YGrow Doc 10 Re_ Feedback_ th&af_sub3=EmailSignature> On Sun, Mar 3, 2019 at 8:28 PM, William Happer b6 > wrote: By chance, Tom Wysmuller stopped by my office on Saturday, and I showed him a copy of the attached draft paper that b6 and I hope to finish soon. Tom urged me to send you a copy, even without asking permission which I would normally do. If you have time to look it over and provide feedback on how to make it more useful to a wider readership, b6 and I would be very grateful. We hope to publish the paper in a journal like Reviews of Modern Physics for readers who are not intimidated by integral equations or quantum mechanics. But we also hope that it will be useful to smart readers without a lot of mathematics background. Key parts that require almost no math are Figs. 9-11, which show how little you change the infrared flux leaving the Earth if you double the concentrations of CO2, N2O or CH4. Table 4 shows the correspondingly small temperature changes needed to restore thermal equilibrium if you double the concentrations. We would be very pleased to get some feedback. Best wishes, Will Doc 10 Re_ Feedback_ Deletion Page 10 pages of non-agency record withheld per consultation with NSC ab a; US. Global Change [9 Research Program LIMATE SCIENCE SPECIAL REPORT 5 Executive Sum mary Fourth National Climate- As-se'ssrnent- i chiume I On?Iine' at First pub'lig?ed 2017 Recommende? Citation -Wu?bhle?, 1351., KLA. .Hibbard,- B. :Dehngeilog-S; Del-mm K. 'I-iayhaye, R. Horton, Km-i??aih, RC, Taylnf, AJM. Wapie. and (LP. Weaver. 2017: Huf?fheEmirate-Sewn? Spec-I'M Kmart; Fmr?h National Valmng I [Wuebblesl Fahey, Hibbard, ll]; Dpkken, Stewart, and 11:5. Glpbal Change Research Program, Washing.an usage pp. Image Credit rival-H are regime; in - like rivers inthe- sky ?that_ transport mostnf-I'he water vapcrr-outgid? of the t'ropi?s. When an ahnospheric river._makes and ?ooding can dfteh- result. Themver features a' natural-Cold:- ir?ag'e 9f cand'itipnslover Pacific on 20 February 201?; helping Gaiifnrnia and-the Ame?can'West em'er'ge'f'rom a.5?year drought 'in stunningfashio'n; 'Ca'lifqrnia melted as much rain in a single deluge as ncrmaiiy- ffalls'in the prec?dingS-montha {October Februarlehe-visu- ?lizaticin was generated. byjesse?llen DhServatury) using data. from the-Visible Infrared. imaging Radiom'tet Suil? {VIIR53'b??the SuqmiIf-Natjinnal Polar-'drhiting Partnership CLI SPECIAL REPORT Executive. Summary" Fourth Nati'on-al Climate Assessment Volume . U. 8 Global Change @Research Program Yakima Editars David I. Damn, Us?. :G'tobal Program - JCF David W. Fahizeratinnal Administration Kathy-A. Hibbard. Natidnal Aeronautics and Space Adm'inistratinn fihntnas'li. Maycock, Canneratiin: Institute-for Climate. and Sateliitcs Nanh'Camiina Brock: C: Simrt,.Cnoperative lnstitate?fnr Ciimatcand? Satellites Catalina Donald Irwnebblaa. National Science Foundation-and-U.5._ Glnha! Change Research Program of Iliinnis Science Sfra?ag'?oinmirtae Banjarnin?ehngelo. Natianal Oceanic and Administration David W. Fahcjr, Natinnaii?manic and Atmospheric? Administration . Kathy'nr .Hibh'ard. Natinttal Aeronautics and Spade Administration Wayne Higgins. Department nf'Commerc? Iacit Kayeriyiatinnal 'Acranauiics and Space Administratinn Energy. Russel] S. Foam?ational Oceanic and Adminiatratinnj . Donald Foundation and US. GinghaIChange'Rcaearch Program .- Universitynf mama .Sn?mm mince on 'Giribni'?hnnge Hagan}: AnnBartasita, Chain-Department of Agriculttire Virginia-Budteti. tin-Chain;- Depart merit 'ofthelntetinr Garakl' Gcernae?', 'ViterCh'air, Dep?arinientni?. Energy Michael Kuperbn?rg. Examina-Dir?ctar. Glabal'Changc. Research. 131113me . loin: Baibus'. Dapartment ochaith and'Human?c?rviccs Bill Breed. US. Agency far Intarnational Picrrc ?ynaHi?iha-Dwartment dl' Commerce Scan Harper,_ Department nf Defense. (Acting) Depar'tntem'nf Agribuituri: lack'Kay-e; National Aamnautic's and Space Administration Dorothy Each, Department df Energy Andrew Miller. US. Enyirn'n'menta] Pratectinn Agency David 'Re'idmilier, .115. Giobal?hangcf?cscarch Program 'Trigg Talley; Department of State Michac] Van Ween, Natitma] Sciencc'Futmdatian Liairpn'ita inc Excwrive D?cg qf-tne President Khaki]? Miner. O?ice of Management and Budget .Reparr madman Man};r thanks to thetaientedaditnriai and design 'team at the Nat innit]: (Semara- for Environmental .(N'CEDCentcr far Weather and Cinnate. bathe-administrative lead agency {Department 9F Comma-rite! National Administratinniand its Of?ce: . Gourdirlmiug Leadmr?lors. National Science Foundation and Global Change of Illinoia David fallacy. Earth-System 'Resear'chlabora'tory Kathy A. Hihbard. NASA Headquarters Leod?uf?ors MFR. 1F. mold._U.S. Army- Corps of Eoglneors Benjamin Dh?o?gelo. NOAA Climate Program?O?ice Sarah Dollerty. Uoiirersity of Washington David'R. Ea?erling. N?h? National Coolers Ifor 'En?roomenlal'lofonooliun lame; Edmonds. Poci?c Northw?l National-Laboratory Timothy Hall. :NASA?Go-ddard 'los'tit?te'for. Space Studies. Katharine Hafhoe. Tom 1th University- Forre?t M. Holman. Oak Ridge Naiional Laboratory .Radley University __Deboral1 Hloominger. Northern Arizooa university Libby lowett. NORA Doom-Acidi?cation- Program Thomas Knots'omNDAA ?Goophysioal Fluid Dynamics Lab Robert-E. Kopp. Rutgers Univgrgity limes R'Koss'in. NCAA Notional Centers for Environmental . information .K?nneth. Allegra. 'for'Space Studies. 1.. Ruby Louog, PacificNorthwe?i National'Laboratory Winslow Maslowski. Naval Postgraduate-School Carl Moors. Ronot? Judith Eerlwitm??AA' Earth System Riasearch' Laboratory Anastasia University- Marional Center for-Atmospheric Research- William V. Odom-'Servicef Patrick G. Taylor. NASA Langley?liosearch Cooler Robert I. Troop, University of Illinois at'Urhaoo?Champaign Russo! S. Vose. NOAA National Hooters for Environmental Infomo?on I I I let Propulsion Lalmra?tor}r Mikhael F. Wchner. Lawrence Berkeley National Laboratory Trislram Dr'Wes't. Science Reviewi?l?tors Linda 0. Center for Atmospheric Research Ross 1. Uriiversi'ty 'of?M aryla'nd Christopher Waiter. USEPA Contributing Authors Richard Alley. Slate-:Unjvorsily Taylor Noam Ocean Acidi?cation Program John Bruno. University of-Nort? Carolina- -Sl_'l_allin Bumnomoceau Acidi?cation Program; Sarah Champion. North'Carolioa National Centersfor Environmental Information - Dwight-GledhilLNOAA Otean'?cidi?tation Pf? . Ig?ti'n Goldst?in. US. Global Chaoge?Researqh Program - Boyin'll-iuong. No.13 National Ce morsfor- Eov'irooment'ai Information- Hari Krishna. Lawrence Berkeley'National Laboratory San Diego.- Fraok'MuHEreKarger. of-So?lh Florida Alan Rhonda's, Davis; Laura State University Liqiang Silo. North garolina-Stare University Eu'gcne Tilda. low; Store University Paul Ullriol'l1 Uhiir?rsit? ofCalifor?ia Davis Eugene 'Wa'hl. NOAA National {footers-for Environmental Information . john'WaISh. Univorsity of??aska About This Executive Sum mat-y. As a key part-of the Fourth National Climate Assessment the'U'S.? Global Change Research Program oversaw-the production of this stand-alone. report of the state of science relating to climate change and its physical impacts. TheClimate-Science Special Report {(28512) 'is-designeel to be an authoritative asmss'm'en't of'tlie science of climate change, with a focus-en'the United States, to serve as the founda? tion for efforts to'assess climate-related- risksa?nd inform, decision?making about responses. In accordancewith this. purpose, it does not include an? assessment'of [iterator-eon climate; change mitigation. adaptation, econom'ie'valuation, or seeietalrresponses, nor does it .clude policy: recommendations.- 1 ofNCNi, CSSR'serves-severai'pu rposee, includingpreviding' Dian-updated and detailed analysis-of the-findings of how. climate. 'changeis affecting weather-and climate act-oar. the'United'StatES; man executive summary and 15' chapters that provide the baitis'For the. dis- cussion-of climatetseience found in the second volume of 'NCAe?it-and 3} foundational informa? :tionand projections for climate change, including extremes; to'improve "matte-end" consisten- cy regional, and resilience-analyses within the-second volume, USSR integrates and; evaluates- the findings- on. climate science and discusses the. uncertainties associated with?these findings. It-analya'es- current trendsin' climate Eha?gE', both human?induced- projects. major trends. to the end of this century-A's an assessmentfand analysis of the. science. important input'to the development of other parts-of NCAIL and their primary" focus on the-human welfarer societal, economic and environmental elements-of climate. change. Much of theunderlying tapor't is written-ate level moreappropriate for a Scientific audience! though the Executive Summary tobe aceessible to alt-reader audience. Report Development, Review, and Approval Process. . The National. oceanicand Atmosphericedministration (NOAA) serves as the administrative- lead agency-for preparation of NCA4. The CSSR Federal Science-Steering Committee [iiSi'Zl1 has. representative's from-three agencies (NCAA.- .ihe National Aeronautics and Space Administra: tion and the Department-of and three-Coordinating Lead' Authors, all of whom Were: Federal employees of. this'z-reportfliollowing a public notice for author nominations in March 52016, the-55C selected the wining? team, con- sistin?gof scientiitts: representing Federal agencies! national- iabttratetiee; universities, anti the private. sector. I l' I nit: case the Memento-id production u'i'the report.- SSE membership was otter: to all agen'cits.? ?the is made up at? I3 ii?deral'ticnarimerits toughness that carryout- nacarchand support the Natnm?s'rcspensr a. meal change. 'Ih: USGQIRP _i_s'evcrsecn by the subcommittee-en nuance-tag: Research Science and-?lechnulogy Council's Com nutter: un' ral sustainability which-in turn, is'overst-tn White House unite ef?cient: and icy The agencict'withit'tUSGERP arethe Department of Agriculture. the Department ul'Cum mam of vacate.- the ni Energy.- the Department Human Service's. lJ'epar'trnritt situate-the Depart mar-t oril'ranspenatien, the. National Aeronautics-mil Space ration. the National Science human-the Institution, and thew-i. Agency'- l?er intematiun at Develoyrnenl. The? first Lead Author Meeting- Washington? DC, in April??lot to-refinethe outline- contained in the SEC-endorsed prospectus and to make writing assignments. Over the course of '18 months before final publication, seven'CSSR' drafts were generated, with each successive iteration?frOrn starot to'sixthaorder drafts?undergoingadditiOnal expert review by the SSC (multiple tin-res), the agencies (multiple times}; the general poolic, and the National Academies of Scienc?s, Engineering, and'Medicine The final review and signjoff-of. CSSR by. the agencies-econ rrerl AugUst.201? under theauspices of the Office of Sci? ence'and Technology Policy OSTP- is rosponsible 'for?the Fede'rai clearance process prior to the final. report prodtiction and .publicrrelease. The Sustained has been deve?l'oped'as'part of the. sustained Nae tional'Clirnate Assessment. process. This-process facilitates continuous and transparent _partici+ potion of scientists- and stakeholders. across regions information and insights to tie-assessed as-they emerge- TheClin?Ia?te'Science Special Report hensive-assessment or" the-science underlyingthe changes occurring in Earth's climate-system, with'a' special-focus on the United-States; I sources Used in this Report. The basedson a as well as a nurnberof other publicly available sources, including ettaluate'd observational-and modeling?. o'fauthorsacarefully reviewed these sources to-ensure a reliable assessment of?the' state of-scientific understanding. Each source-of information Wasdetermined to. meet the four parts-of the quality assurance gui'dante provid? ed toauthors '(fol lowing the approach from the Third National Climate'Assessmen't): _1)-utility, 2) transpar'vencgri and traceability, 3} objectivity, and integrity and. assessed and information from technical reports pro? the rigorously-reviewed internatiOnal assessments from the Intergovernmental Panel on Climate Change}; reports of the NAB-and its. associated National. Research Council, and various regional climate impact assessments, confer?- ence proceedings, and government statistics {such aspopu'l'ation censusan'd energy usage). ?Aulhor. responses l'u'ceniments submitted. as part uf'lhe Public Comment Period an'd'a response iu' the review conducradby'NAS turn be found on {stimuli} litglobalchangelgowdownloadu. Ire-atment of .Untertaintiesr Likelih'oods', Confidence-rand Risk Framing Throughout this reportls assessmentof'the scientific understandingof climate change, these- thors'have assessed to the fullest extent possible thestate-otLthe?art understanding of the sci-- ence resulting from] the information in the Scientific literatUre to arrive-at Conclusions as Key Findings, The approachosed to extent of understanding represented in. the. Key Findings-is, clone th rough two metrics: Confidence in the validity eta-?nding based on-the type, arnoont, quality, and .mnsistency of evidenceisuch as mechanistic- understanding, theory, and. expert range, and consistency of-roodel projections; and thedegreejof agreement within the body of literature. Likelihoodor probability 'o't'an effect or-im'pact occurring-isbased on measures of uncerr tainty'express'ed probabilisticallp {based on the degree of. understanding-or knowledge, _-resulting from of observations orjrnodel results or on expert-ii: dgment). Assessments of 'confi dence in the Key Findings-are based on the expert judgment ot'the author teatnr Airtho'rs provide supporting evidence. for. each of the chapter's Key Findings in the Trace- ahle Accounm. Confidence is-expresiead qualitatively and ranges from haw confidence {incon- clusiveevidenCeor disagreement-amongexperts}to very high confidence (strong evidence and high consensus} (see table on inside of back cover for the'fuil' range]. Confidence. should not be. interpreted- probahilisticallyt as 'it'is? distinct from-statistical likelihood, in this neport, likelihood is-the chance of occu rr'ence otan effectorimpactliased .on measures of uncertai'nqrexpressed probabiliSti'Cally (based on statisticalanalysis.ot observations or model results or .on'espert judgment). The authors used expert- judgmen't'based on. of the literature assessed to arrive at 'an estimation of the likelihood that 'a particular 'ob?rved effect was related to human contributions .to climate change or theta particular impact willoricur within the. range of possible" outcomes, Model uncertainty is an- important-contributor to uncer- tainty in climate projections, and includes, :bot'i's not restricted to, 'Ithe-uncertainties introduced by errors in the model?s, representation of the physicallrand bio-geochemical processes affeCting the climate-system as well again the model?sresponm to external: forcing, Where it to report the. likelihood ot-particular-impactswithin the range of possible outcomes, this report takes 'ajplainelanguage approach .to expresating the airport-judge m'ent of'the; chapter the best available evidence. outcome-termed "likely? has at. least sass. chance likelihood greater than about 2-of 3 chances),- an ontcome. termed ?very likew," at least-a 90% chance {more than 9 out of 10 chances}. - - 1 1 u- rot-3T.? a; mlr- must-regs Highlights of'the Global Change Research Program Climate Science-Spetial Report The climate of the-United States. is strongly connected torthetihanging global climate. The-statements below highlight projected climate-changesfor the United States and-the globe. Global annually-averaged surface-airternper'ature has increasedby-aboot 13F. over the last 115 years period is With wannest in the?hi's'tor'g of modern .tlirilizatlon. The last-few years have also. seen weather extremes. and. the last three yearshave been the. warmest-years on record for the globe. These trends'ere expected to .continue. over climate timescales. extensive evidencethat ?is extremely likely that .luiinan activi- ties. especially eoiissioos of greenhouse'gases, are the dominant tense of since-the'midezom :entury..For the Warming over the last 'century..there is noconvincing-alternative explanationsursponed by. the extent of the obmrvational evidence; ln-adlditlon' to.warming,_ many other aspects of global ctimajte'are' changing, primarily in response to hu- man aetiirities. Thousands by researchers around the world have documents- ed changes In surface. atmospheric. and oceanic temnetatoresi- melting. glaciers; diminishing. snow hover: shrinking sea ice; rising in was; oceenatititl?ication; antiincreasingatmospheric- water vapor. For-example. global average sea 'l'evel has ri'sdn by-abmit 7?3 inchessince' 1900, with almost half {ahoot 3 Inches} of'that' rise occurring since 'i 993. Human-ce'used-Ciimate change has made asubstan- tialtontrihution'to this rise tole- rate-of rise that is greeterthan during any pretetiing senior}: in. at least Global -'se_a lesrelrise has a'irinitlzg.r affected the United states;- the incidence of ?ooding is'atcei'e?rating In more than 25 Atlantic and-Golf toasticitie's. Global-averagesea levels are expected to-tontinne to-rlse?hy ail-east several iotl'ies intiie next 1 5 years. and. by ,1?4_feet by 21 on, A rise. of-as much as 8' feet by 2-1 so cannot be ruledoot-[Sea level rise Will .behigher than the global average on the-'East'and Gulf Coasts of the United States. Changes-in. thetheract'eristics of extreme eventsare particularly important for human ?ture..agriculture.- water- quallty-and quantity, and natural ecosystems. Heavy increasing in intensity and-?equoncy across the United .States-and' globain and is expected to continue-to. - crease-Sim largest observed changes in the?iUnited States have .octiJrred'in the Northeast. 1" nil Err-[Jar Fit-?fir; gri'?il'i .f'i?rli Heatwatres have become m'o'refrequent in the United States-since the 19605, while extreme. cold teaspetatures-and cold wavesare-less hot years are projeCted to be- come community the" near future-for the United States. asannual average temperatures continue to- rise.=Annual average temperature over the. contiguous United States has Increased by (1 :01) for the the nextfe?w decades [202.1 +2050}.- a'n?n'ual average temperatuires are: expected eo'rise [weapons-15?F for the-United States. telatiite to the recent past Leverage from 1 under all plausible ?ltrate climate scenarios. The Incidence of'large fores't?fires in'the States and. Alaska'has increased since and to further increase_._in those regions profound-changes to regional - Annual trends toward earlier-spring s?nownack are already-affecting water re sources in the western United 'states to continue. Und ethigher scenar- ?ios. and assuming no change to currentr'water resourCes long?duration hydro- logical-drought-is increasingly possible hefore'theendjof this century. The magnitwe-of beyond theneut'few decades-will depend primarily on: the amount. ell-greenhouse gases {especially carbon'diostidei emittedglohally. Without- major-reduc- tions in emissions; the inc'reasein' annual average giobaliternperatu'i?e relative to pre'industrial'time's could reach EFF. more by the enclof this-icontury. With significant reductions in .entissions,.the increase In annual average global temperature could be global atmospheric carbon clienticle concentration has now passes! 400 parts per million {ppm}, a-ievel'that lastoccurred about 3 million years ago. when both giohaliaveragejtemperae ture and sea level were significantly higher than today. Continued growth in emissions over this cantaty and'be'yond would lead to anatrnospheric concentration not experienced in-tens to hundreds of'rnillions-of yeare?There is broad 'consensus-that'the further and the'faster- the Earth System is'_pu'shed towards. warming. thegreater the-risk of unanticipated changes? and impacts, sorne of Which arepotem- tially large-and'irreversible. The observed increase. in carbonemissions over the past 1.56.20 years has'been consiStent with higher Emissions pathways. in antenna 201 5, emission growth rates slowed as economic growth became less this slowingtrend continues, however, it is not yet ate-rate that- would limitglobalgaverage temperature change-tome? beioW'BE'F (TEE) abate-preindustrial 'ieveis. ?ecorninended Citation forthe'Full Report - - 201?; Climate science Spec-lei Report: Fem-fit Ne?ifoiini??intoie-Assessment, Volume [Wuebblesj 3.1., ow. Faheys lea. Hibbara; DJ. Del-tken, egc. SteWart,- and T.K. .UL-S. Global ChangeRestearch Program,- WashingtOn,,-DC, USA, 470 pp. .L-. 1931 ['rt FlirE- 2 I I Exe cutive umm a ry Introduttion. New observations and newr research have increased our undetstanding of past, our-remit and his tune climate changesince the Third National Climate Assessment (NCAS) was-published ,in may-2014. This 'Ciimate-Seience Special Report its-designed to tion and build "on the-existing body of science int-order jto-sumrnarize. the Current'stateoiitnoWI- edge and provide. the scientific foundation for the Fourth National Since NCAS, stronger evidence has emerged for continuing, tapidrhumaneeaused' warming of. the global _.a_tmosphere and-ocean'ifhis- report-concludes that "it is extremely likely that-human influence-hasbeen'the dominant-pausedthe-observed For- the warming-over the-lasteentury, there-is no convincing- alternative explanation- supported by theextent of the observational evidence.? The last few years-have also seen record-rhreaking, climates-related weather-extremes. the three warmest years on recordffori'theglobe, and. continued sea ice. These trends are expected 'to continue. inthe-iUture timescales. Signi?cant advances have also been made'iri our understandingof extreme weather-even ts and how. they roiate to inerea'sirig global temperatures and associated the cost of extreme events-for the United States has exceeded $11 trillion; therefore, better understand ing- of'the. frequency and Severity of'these events in theeontext?-a changing-elimate is. warranted; Periodically taking stock-of theturrent state of knowledgeaboutclimate change and potting new weather extremes; changes insea- ice,_ increases in ocean? temperatures, and ocean acidifi? cation into context en'siures'tha't- rigorous, scientifically-based information 'is- available-to inform dialogue and decisions-at every level.- This elimate science report. s?e?rvesas'the climate scienoe' foundation of the isgenerallyr intended for those who have technical background in elimatescienoe; In this Exeeut'ive summary, gray boxes present highlightsof the'main report, These arefollowedby related res-providing more sEienti'fic. details. The summary material tin-each topic preseritS'the most,salient..pointsof chapter'findings-and therefore represents only-a subset of the report?s content. For more details, the reader is. referred to the individual chapters. This report discusses-climate trends and findings at sewErai' scales: glob'aL nationwide for'the United States, and forten specific regibns {shown in Figtirel in "the Guide to the Repert). Astaternent of scientific confideneealso follows-each-point in the ER: amide-Summary, '1?heconfidenee scale'isdescrihed in the Guide to the Report. At the end :of the Executive summaryandin Chapter 1:"Our Globally Changing Cl imate, there i's-alsoia summary box highlighting thelmost'notahie-advancies and topich since NCAS and since the 2013 intergov? emrnen'tal Panel on" Climate-Change Fifth Assessment-Report; 3 fit.) Hf'ixrt?. 513mm Summary] 13%; mints it Hem-r1 -. Glebal to Rise Long-tent: temperature nbaervatidnafare among the most consistent? and'widespread evidence at a warming planet. Temperature all} its Idea} averages .andextrernes) affects 'agricuitural productivity, energy 115e,.human, health, water resources, infraatructure, natural- ecOsyStems, and many ether essentialaspeeta of society and the net-Ural environment._ Recent" data add to the-weight of eVidence-for rapid global-seam warming the daminance-ef human causes, and theexpetted "continuatien of inerea'sing temperatures, including-mare recerdgeet?- ting extremes. 1) and Projected Eta-bat Temperature mm'msinmha mm_man m:wy; 21:amassed-:01 5.5mm of; the yum you: an last 17mm (1998 was-?u Won). ?31: I: Fig: em 0 Global annual average. temperature (as calculated from instrumentai records-i"- over both land and oceans) has; increaaed'byi'mme than the period at'ive te'1901-1960; the linear change over the entire period from-IQ?l?2?16 is {very high carg?dence; Fig, Longer-term "climate. retards over pa'et centuries and millenn'ia indicate that. average 'temg?eratures in recent detadee; ever- much of the world have been much higher, and have risen faster during this time peri? -od than at: any time in the-paHtLIGD' years-or more? the time period for which the 23103:)? a] distribution or surface temperatures can be recens'hucted (high. con?dane?; (Ch. 1). Giebal Temperatures Continue to Rise Giehal Land and Gwen Temperature-Anomalies Annual 1teach me 1921} 1940 1950 Issue mm mu ?115 -a.5 an. as in 1.5 2.0 ?as are Figure 55.1; (are .Glebal annual average temperatur6=h'as increase'd by mere than rees- 190161960. Red bara'shaw ten'Ipetaturea that wereahaue the 15G1a1960 average. and bluehars indiCate temperaturee- eaten the average; {right} Suriaee'tern paramirei'changei?n ?Ff! for the period-19354915 relative ta 19131-4 960. lit-ray.r indicates missingaata- me Chapter 1 far-new :iz-ae: in'i'ei. 4 "int-:1 Eli-letter: - Many-lines of evidence demonstrate that-it iarextreinely likely that human influence .haa'been the dominant. cause-of? the-observed warmingaince?the mid~2llth gentury; over the leer-Cen- tury, there? ere noiconrrin'eing alternative explanations supported by theex'tent 'ef-the obser- vational output natural tiaria'bilit}; can only eontribute marginally to the obeeI-ved changes in elimateoher the and there is noeonyincing evidence for natural cycles in the observational record-that eculd expla?tn-the-obeerved-chang- esinclimate?.? 1) '0 The-likely rangeolf the humah contribution to the global, mean temperature increaae over the-period 19513-2010 to (he? to the 'central estimate; of the obe'm'ved warming of lies-within. this range (high con?dence). This translates 'to ?a likely human contribution of 9292??! 23%. of the observed 1951?20-10 The likely contributions-- of natural forcing and interna'llva riabilityrto global temperature change? over-that period are. (Ch. 3; Fig. .If Natural variability, .including'El Ni?o events and other of oceannatntou eohere interactions, impactternperanlre and precipitation, especially? regionally, over times- cales at ?global influence of natural however, is limited. to a email fraction of observed climate trends? over decades. (Vary-high ron?dahce} (Ch. HUI-nan activities-Are the Primary Driirer :of Recent Global Temperature ?Rise 3.5 3.0- 2.5? ?2.0 .145 till 3 Di?i Radiative-Earner; twee}. watt-m1 '1 - I I I Human-mused Solar - volcanic?. ?Figure Bani Global emuateuerage radiative rummage-rem 1,750 to 2011 due to mean adivi?ee. changes in total enlar- Static bare indiaere ?uncertainty injeaet Radiative forcing is a measure urine in?uence a factorleueh gee hash-?t changing the global balehce' of incarnate-arreeutnoing energy-Emma foreioge greanr manage-(positive {orange} pmduea climate waning; tunings-less than zero tnegatihe tutelage] prodrioe dimate mating?Over this? time 93er searches baa oeoiltated on appmemeeryen 11-yearcyele between enema +0.19 vane. Ream farting dueta main entriesione? isalwaysregative {cooling} 'arldeen be very argeiwnediately follohiihg signi?cant swarms nut-e snort-lived. imam? era. the reggae?tome fbreina hitched tie-emit at. Mt. Tambora in? 1315 (-7115 lath-F}; This farting declined to -4,5 Wm: in ??316; and ?to due to human aetivtties'. in contrast has bacoming inoreaein'gly positive (warming) einoe about at-en accelerated rate-?since Elliott! 1970.- There are also nauaalrarietichs in ?Mature-and other nan-late variables which 'op'erate?an annual to'deeadel time- nemral-vahaility m?mme-veryiit?eto dirnate-trende-aver decades and beget. Fem-2.6m Chapterz. SeeCheptar'Eformere'detalte. . n. -. 5 aura. mu? arm.- Executive summary Climate Balance peter Remit Global climate-is projected'to continue._. to: changeover this centm'y' and beyond. Themagni- jtu?de of climate change beyond the-next few detade's willdepend primarily och-the amount. of. greehhouse {heat?trapping) gases-emitted globally and tan-the remaining uncertainty in the sensitivity of Earth?s climate to those emiss'ionsIvery high 'cen?cience); With signi?carit feduo- ?own-in the'emis'siotts of gr?erlhottse. gases, the: global annually averaged temperature. rise co'uld'be limited less. Withoutmajor reductions in these-emissions, the in? crease 'in annual average global temperatures relative to pteindu'strial..times could. reach at more by thei'end-of this. cenmty. (Ch 1; Fig. E53) If greenhouse gas concentrations were-stabilized at wee-current level, existing concentrations would'commit. the world. teat-least an adclitional warming-otter this century relative .to the last faw-"deeadES (high cen?denee'jn'continued warming, medium con?dence in amo'utit. [Ch 4) Foorth?atnonal Voi'u'me I. 5 mais- {tit-? rir??fi-l Summary! Scenarios Used inthis Assenment Projections of ?xture climate?ond'itioosnse a range of plausible futineahenarios.? Consistent with previoos practice, this-assessment relies on Scenariosg'enerated for the Intergovernmental Panel on Climate Change Ip'cc completeditslast assessmentin 2013-2014. and its based on updatedscg. narios, namely four?representatlire concentration scenarios are nurhberedaccordr- lngto changes: in radiative forcing in 2100 +63 and +3.5 watts per square meter is a measure-of, the Influence a factor {such osg?nhousegas :emissionsi-has in' changing the-global balao'ceof incoming and'outgoiog energy. Absorption by greenhouse . gases infrared-energy radi'ated from the surface laws to warming of-ttie.surfaceand atmosphere. Though multiple emissions pathways could ,Iead'to't'he same 21.00 rad iativeforcing value. an associated-path. wayof C02 endotl?re'r' human-caused emissions of greenhouse gases. aerosols, and air pollutantshas been; selected" for each RCP. BCPB.5'implies a fixture-with continued high. emissions growth, whereas the other REPS represent. different pathways pfmitigatingemission; Figure-?53 Shows these-emissi'oi'ls pathways antithe- ._corresponciing Greater Emissions Lead to More-Warrning Aggie? Projected Global Ternpe'ratui'251* E: l tower seam . .3. ml enmemaidtm'sl .3. 5 -: 15- 4. 51's.! a 5 ,i a tan-o 155s soon sass 210a 1901 -.1951' zoom 25512 2101 Figure 55.3: Thetwo panelsabove show annual historical and-a range of praises-fume .oerbm-smissions'in- units ot?gigatons ottoman-{Gm} per year (left) and thehistorioei obsenred-ano fature'tern'per'ature'ol'ienge that would result fora range of?futUresoena?os relative to, the 1901+195u average; based on the {tootsiestim'ate {lines} and-e range (shaded'areas. two standard deviations) assimolataooy the full suite of CHIPE genital cliinate By soot-2100. in global Mean Emberatore unearths even lower- soenario green}, under the lower soenorio was}. ashes"!= was; the mid-high scenario-(Rams: not showniano under the higher Wit. formers datoils on'mese'sOe- natios ano'intpiioatiorss; Based on'Figwe-u in Chapter at. ExecutiteSummai-y saga..- saga-i Changesin?bsersed and Projectod pm-iwtpnioaodli'mummimto {ch Sifts, Anm'JaI average temperature: over the contiguous united States has increased by (tit-WC) for. the period 193642016 tEIa?ve to 1901?19ti?-and by .1 based on :a lih?car regres? sion for the {very Sui-face and satellite data-are consistent in their depiction-of rapid warming -5ince.,1979 (high Pa'leoi-temperamre evidence shows that recent detadesiare'the'warmest of the past {medium co??derice). (Ch. 6) Annual a'veragetemperatu're overthe-contiguousUnited States is..prokcte.d to rise (very high con?dence). Increases of about are projected'ior the petioldfz?zl ?2050 'i?e'lative to the awerage [torn 19?6?2005.it1 all scenarios,- implying recen't'record-setting years may-- be "common" in the next few decades Much larger rises are projected "by late century- (2071?2100}: lower scenario Tar?11.991?" in a higher scenario {high con?dence), (Ch. (is-Fig. - '_1n the United States-the urban heat island effect results-in daytime temperatures higher an d'lnighttime' highe urban areas .than'in rural -_areas, differences. in ?humid regions (primarily in. the eastefn .Uniteti'Stat'es) and in cities with larger and dense: populations. The-Urban heat island effect will strengthen in the tutor-e asth'e structure. and spatial extent-asweli as population density of "urban areas change and grow (high. con?dence); (Ch 10) . is. if comma 3 In 31m}: Signi?cantly Mere-Wanning Occurs-Under Higher Greenhouse. Gas-Geneentratieni "Scenarios Mid Lewer ScenarietRGPe?l we? - -- he?. . .1 Higher Seenaiie .452: .- Fihaneein Temperature (?Ft 2 4 5 a ?1,0 1.2 14 "16 18 Figure .4: These maps-snow-the-ptdiected changes": in. annual average temperemree for unit!- and late-Etet'cenmry tar two futurepe?mayea. Changes are-the between the average pmjected't'emperatureefer midgeentury (21333?2065: top); and late-cerium {zen?2099; bettern}, fer' the. See Figure-?gr-inChaprer_ form". Hematite. Many'l'emperature and Precipitatien?xtremes Are Becoming were Comma? Temperature and p?reeipitatibn extremes can affect wa?ter'quality and availability agticuiturail preductivit?hutnan health, vitalinfraetmetui-e, icenieecesyeteme-and.epeciee, and the like- lihood of dieaeters.50me extremes have already became more frequent; intense; or efillonger durati'en, and many extremes are expected to continue-to. increaee-er-wersen, presentingeubw. stan?tial challengeefor built-,_ agricultural, and neural-systems. Some storm types-such as hurri- canes. temadoee, and winter Stomea're else exhibiting changee- thathave been linked to climate changealtheughthe current-state of penn?itdetailed understanding. Set}: Amati-"it I '9 at: P: aid-5.71m Eieteiit?ummary I 91"151?11255115111111 155111.11: 51115115115111.1192: in Extremes There have hem marked change: the-51111113115115; Uriited States. ?premium 1115711195 1511mm. 5. Rs. 55.51 The: 'fr5q1151'1cy of cold wave-5 i155 decreased 151155 ?the early 1-9005 and the frequency of heat waves 1155 increased 55155 the ?mid- 19605 (the Dust Bowl era of the 19305 remains? the peak per-ind for. extreme [1551' 111 the United 551155}, (Very high con?dence}, (Ch. 6) .1 The? fr'eguehcy'a'nd intensity at. extreme heat and heavy precipitation events- are increasing. in 3111115t continehta'l reg'ien'5-11f the World (very 11131119551515). tr?nde are 5555i5teht- with expected physical reapdnses t5 5 Warming climate. Climate model 5tudi55 are air-10 cen5i5tent with these ta endemstimate the 11b'55rved trends 55p'eciaily for the-increase In extreme precipitation events {115131 high ceryiiderrce.? for temperature, high can? deuce for-extrErne precipitation}. (Ch. I Record-Warm Daily Temperatures Are Occurring Morefo?en 31' I 951595?? Regard Highs I More Daily Record-Lem- ?53? 1 .i Re?t: 51.1311in 15111111111111.1111 Records939 1949-1959 1959 1979 1999 1999 2999 2919 Year .A A .1 Figure ?5.51 Dheewed changee' in. the 55511115555 5f r'ecerd- earring daily temperatures 111 the contiguous United States. Red bars indicate a- year with there daily record: highs than dairy regard 1:15; while him here indicate a year with more record laws than highs. The height at the 1151' indicates the retie o'f' recerd highs to Iowa (red) or 1111515115 [51115151 high'e. {blue} For eherndle. 'a rain; 11f'2: 1 tare hide bar means that there were twice. as many. daily laws as daily record highs that year {Figure Figure 8.- 5111 Chapter 3. Ft.- .11155:1111:125121.11e' 31955552511. til-.1115 I. 1i} ?pr?t-ml WMEVE-Summaly. mm: {Ch Extrerne Precipitation Hes 5311' Maximum Daily- Precipitation 99m Percentile Precipitation- - . (1901?2515} . ?(1953?2016) Number of Sam. 2 Bey Ewente Number of 5941*. 2 new Events (19901-4013) case-ems) to 11-9 10-19 '20;sz 30-39 40+ Figure ES 5: These. mepe' show the percentage change in sewerei metnce of extreme precipitation by MGM region inciuitiing {upper-b51519 maximum daily precipitation in certeecutiwe 5 -yeer- periods: (upper right) the amount of precipi- tation fa'liin9 in daily ewente that exceed the 55th percentile of all non-zero precipitation days '{top 1% of pit delay precipi- tetion ewentei, (lower Iei't) the number of 2-day ewents with e. precipitation total exceeding the Iergeet 2-day. amount thet is expected to come on mega only once ewerw 5 years. as calculated ower 1551?2515: and (tower right) the number- cfz-dew ewentewim e' precipimtion totes exceeding the Ier9e5t 2:533,- amount that is' expected to occuri 'on' average. onty once ewerjr 5 years, as calculated ower. 1955-2515. The number. in each black circle lie the percent change owe:- the entire period. either 1501-2515 .or 1955?2515Note thet?ieeke and Howrah are not included' In the 1551-2015 maps owing. to 'e tacit of observations in the eeriier. part of the EDth century (Figure. ermine: Based on ?gure 4 in Chapter it. 13.11.. retailer -. 95m .- r; Executive'Summarr Clii?l?ate then-"e Recent droughts and associated heat waves have reached racord intensity in some regions of the United States,- however, by. geographical scale and duration the Dust Bowl era of the .1930s remains the benchmark drought. and extreme heat event in the historical record. Wary high con?dence} (Ch. .3). Northern Hemisphere spring snow coverI extent, North America maximum snow depth, . snow orator equivalent? In- the western United States, and extreme snowfall years in the south. em and western United States have. all declined, while extreme snowfall years in parts of the northern UnitiedStates have increased (Ch. There has been a trend toivard earlier .snowi?nelt and a decreese in- snowstorm frequency on the southern margins of chronologically snowy areas con?dante). Winter storm tracks have shifted northward since 1950 over. the Northern Hemisphere con?dante). .. Potential linkages between the frequency and intensity of. severe. winter storms in the United --StaItes andaccelerated warn-ting in the Arctic have beenpostulated, but they are complex, and, to some extent, contested, and confidence in_-Ithe' connection is currently low. (Ch. 9] Tornado activitj,I in the Unite-cl States has become more variable, partic?ular?l}I over the 2000s,- with Ia decrease In the number- of- days per. year with tornadoes and an increase in the number- oi tornadoes onthese days (medium, con?dence}. Confidence' In past trends for hail and severe thunderstorm is late. (Ch. 9} - Projected Changes in Extremes The frequency and intensity of extreme'nhigh temperature events are areas certain. to increase in the future as global temperature increases (High InII?deII'c'el. Extreme.- precipitation events will their continue to. IncIease- in frequency and intensity throughout most- of the worid thigh remittance} Observed and projected trends for some other types- of. extreme events,- such. as floods droughts,- and severe storms, have more variable regional characteristiot. (Ch. .1) Extreme Wm the United maimed whereas. wed mien-Ian (mil Both eitremely cold days and extren?Ie'Iy Warra- days are expected to become warmer. Cold waves are predicted to become less intense while heat waves will become more intense. The. number of days below freezing Is projected to decline while the number above will rise, tVery high con?dence) (Ch. IS) The frequency and intensity of heavy precipitation events in- the United States are projected to continue to increase over the 21st centLII-y (high Con?dence). There are; however; import- ant regional and seasonal differences' In. projected changes' In total precipitation. the northern united States, including Alaska, 15 projected to receive more precipitation in the winter and spring, and parts of the southwestern United States are projected to naceive less precipitation in the winter. and Spring (medium. confidence). (Ch. Halt?I Assessme?; ?J?IUlui'f'ltT- 12 4 re two'e'mif 1. The frequency andiejeverity of land falling ?a?tmoepher'ic on, the-U5. of'the. typical shonack and annual-pre- cipitati'on'in- the region and are aesoCiated with severe ?ooding evente'1will'increaee'as a result of increasingevaporation-and resulting higher atmospheric ?Nata-"vapor that occurs With in- 11m con?dence.) (Ch. 9.3. .1 Projections? indicate large declines? in snowpack'in ?the western united Stateaand shifts to: more. precipitation falling. -a31rai'n- than snow in thecold scasm in many ?parts of. the central and eastern United con?den?ci. (Ch, If substantial reductions in western US. winter- snowpack areprojected as the cli-. mate wanne.. Earlier spring melt and heduced Snow water equivalent have been tot-finally to homan~inducediwanning(high can idericc'} andiwill I?Ery likeiy'be exacerbated as- the. climate continues towarm {very-high cmg?de?ce). Under higher scenarios; and-155111111113 no changejtoeurrent water'tesources managenient, chronic, long-duration hydrological drought is increasingly possible by the end-of this high corrJidcncEJ-zwh 8} as 111. dim mem?n h1gl'1ar mites. Mum Milan '1 The=.hutnan effect on droughts evidenceis'found for but muchleiridence is found for-a hit.- man - influence. onsurface soil moisture deficits due to increased _evapott'anspiration caused'by higherteniperam'reS. (High _cmy?jience) (Ch. 3} I .1 The incidence of large forest fires'in the weetei-n' Unit?d-States and Alaska has increased since: the and is projected to furthea'increaae'in those regions as the cli- mate wann's, with profound changes to certain-Ecosystems (medium commence}. 8) -. Both physics and numerical modeling-simulations generally indicate; an increase in. tropical cyclone 'i'nz'ajwarmet world, and the models generally show an increase in the new 'ber of' very intense-tropical cyclones, For Atlantic andeaste'rn North Pacific hurricanes; and weeternlNorth Pacific typhoone,. in precipitation tateelhigh con?dence} and intensity [medium coii?denceh The-frequency. of. the most intense of-these storing in .pro- -je_ctec1 to increase in the Atlantic and weetem' North Pacificiiow con?dence) and in.'the eastel'n North Pacific (medium con?dence), 13 - In}; Giurbai I .i?J'i?cn net! '11 Executive-Summary I Box ES.1I The Connected Climate System: Distant Changes Affect'the' nited States Weather conditions and the ways they vary across regions and. over the course of the year are. influenced in the United States as elsewhere, by a' range of lactate including local conditions [such as topography and urban heat islands). global trends isirch as human- -causerl warming}, and globaI and regional circulation pat- terns, including cyclical and chaotic patterns of natural yariabillty within the climate system. For example- during an Nir'io year.- winters acIoss- the southwestern united _States are typically wetter than average. and globaI tern paratures ?-are higher then average. During a La year._ conditions across the southwestern Unit-'- e'd States are typically dry, and there to ads to be a lowering :of global temperatures {Fig ES El Nine? Is not. the only repeating patteIn oi natural yatlability' the climate system Other lmportent patterns. in clude the North Atlantic _Osciilation? Annular Mode particularly affects conditions oh the U. S. East Coast. and the North Paci?c and Paci?c North American Pattern (FHA), which especially affect conditions In Alaska and the US. West Coast These patterns; are closely linked to other atrno- spheric circulation phenomena like the position of the jet streams. Changes in the occurrence. of these patterns or their properties have contributed to recent U. 5.- temperature and precipitation trends. [medium confidence} although confidence Is regarding the size er the role of activities In these changes {Ch 5) Understanding the full scope of human impacts on climate requires a- global focus because of the intercon? nectad nature of the climate system For example. the climate of the Arctic and the climate of- the conti nerital United States are connected through atmospheric circulation patterns. While the Arctic may.- seem remote to most Americans the climatic effects of piano rbatlons to arctic sea ice, land we surface temperature. snow coy-.- and permafrost a?ectth'e amount of warming, sea level change, carbon cycle impacts. and potentially even weather patterns in the lower 43' states The Arctic" Is warming at a rate approximately twice as fast as, the glob- al average and if it continues to warm at the same rate._ Septembers will be nearly ice?free In the Arctic Ocean- sometime- between now and the 20405 (see :Fig. The important influence of arctic climate change on Alaska ls apparent: the influence of arctic changes on U. 5. weather over the coming decades remains an open question With the patentiai for significant impact. (Ch. 11.} .Changes in the Tropics can also impact the rest of the globe including the United State; There is growing evidence that the Tropics have expanded poleward. by about 770 to 290 miles in each hemisphere otter the period 19F9-2?09with an accompa nying shift of the subtropical dry zones, midlatitude Jets. and storm tracks [Medium to high con?dence}. Human _actiyittes have played a role In the change {medium con?dence}. although con?dence Is presently law regarding the Ina-gnitude of the human contribution relative to natural variability (Ch. (continued'on next page) arm-enter: '14 t'i'i'E'di-t? ii?. 5.3- Harri}. fill summary Box 55.1 (continued) Large-Scale Patterns {if Natural 'Variahiuty us; Climate__ .- Typical El Ni?u Winters . ?a Whiter . 'Extend?d'Pam?cJet . . $1.328 m. .ar?phnecl sigma tract; Typi-i La Ni?a'i'i?niei's Figura E53: This ?gure illustrates the typicat January-March weamer anbmalias and ammharic .cirbula?on during moderate to strong (tap) El Ri?e and {ham} La Nina Triage in?uences aver the Ur?ted States after: occur most during that card season. From Figum 5 2m Chapter 5. 1'5 Shmmafy I 5; em me Del" Erat-Ii-tegny- Oceans ?reRisimg-i More Acidic Oceans. etcupy-two-thitds of the planetfesu'rface;and- heat-uniqueemaystems and species. in- cluding thoseimpertant fer-global Commercial and subsi'etence fishing. Understanding climate impacts. on, the-oriean and the ocean-'5 feedhaeks to the-climate Eye-tern iec'ritical for hensi've understandih33ef'current and Future?changes _in climate. aloha! Omani-teat mam .- Mamet: made-?1mm Gcean heat cente'nt has inereaaed ,atai'tdepths since the 19605 and eat-face water-shave warmed by about t- per century globail'y Since 1900' tel 2016.. Under higher- seenariae, a global increase intaverage is protected-M2100, (Very high con?dante}; {Ch-13} I Global and Regional Sea LevelRise 3an IWIWIMJW since waitwhighcm?du?l- .12} - Human?caused'elimate'changehaa made a Substa?tiai centtibution to GMSL-rise since-1900 (high can?d?nee), Contributing-to a rate-DE tire that 15: greater than during any preceding centu- _r}f in at Iea'st 2,800 greats (Ch, 1-2} Fig. E33) Relative to the year 2000. GMSL is very likely to rise by 0370.6 cm) by 2030, 0.5?1.2 feet {15?33 by 2050,.and 1.0?4.3 feet 52100. (very high cwy?fdeuee low- er bounds: medium con?tienee in upper and 2050;'Iew5'contidence 'in upper boundefer. 2100); Futere emissions-pathways have. little effect CMSL'j-iee the ?rst half of the century, but-significantly affectproiectiGHS for the sapond 'hal'f'ef the century {high con?dence}. l(Ch. .12} Fag.- in Nehr?nnm titan-171: :I'gl give 1- '16 2'13 I I: I: u: testis: fiesta i I EttwtireSummaIt Recent-Sea L'e'uel Rise aatestior Otter 2.000 Years Global Mean Sea Levet (feet) -soo 6 Sim who Aztec YeargiCE-i Statesman sea-sel?ess . 1300 1350 __1900 was zoos 2050 2100 Figure ES 3: The- top panel shows observed and reconstructed mean sea ie?eel for the last 2 560 years. The bottom panel Shows proj?tted mean sea leiiel for at: future aoenarioe. The. eik- scenarios?spanning a range designed to inform a variety of decision makers?extend from a tow amnesia. eonsistent with continuation of the rate otsea lava! rise? over . the last quarter century; to an extreme scenario assuming. rapid mass toss from theAntarctio shoot, Note that the tango on- the earliest- axis in the bottom graph' Is aoprokirnatew ten times greater than in the too graph. Based on Figure 12 2 and 12.- 4 Chester 1 2 See the their: report formers details? 6 Emerging science regarding stalziilitj,r suggests theater higher-scenarios,- a GMSL rise Exceeding-:8 feet rn-be'? is physician-y. possibiet although the probability of such an extreme'ontcome cannot currently be Regardless intermission pathways itis extremely-likely. that CMSL use will continue-beyond 2100, (high con?dence-MChI 132) Relative sea level rise in this centuty will vary along coastlines due, in part- to changes' In Earth's gravitatitinal field and rotation from melting of- land ice, changes In ocean Circulation, and vertical. land motion (very high confidence} For almost all ?lters GMSL rise scenarios rei- a?tive-sea lavel?rise is .lik?iy to be greater than thE'glob'al_average in the US. Nottheastiand the western Gulf-of Mexico, in intermediate-anti- low GMSL-rise scenarios, relative sea ten-re] rise is likely to be less than the glob?ai average in much of the Pacific Northwest and Alaska Fer high; GMSL rise scenarios relative sea loyal. rise is likely to be. higher- than the global average along all [1 coastlines outside Alaska. Almost coastlines experience more than giohal mean sea levelrise in. tesponse to Antarctic Ice loseancl thus would be particularlyaffected und?r ex- treme scetiatiosiin?voitring' substantial'eotarctic 12)" 1? Iii?ru?ii'r? gin- 5001mm I il?ii'iis'ie ?neriai ileum?: Coastal Flooding 5 A5 sea level5 have risen the number of tidal floods each year that cause minor impacts (also called '"nuisaIni:e floods?) have increased 5- to 10-fold since the 19605' In soveral coa5tal cities [very high con?dence}. Rate5 of increase are accelerating in over 25 Atlantic and Gulf' Coast cities (very high con?dence}. Tidal flooding will continue increasing in depth frequency, and extent this century (very high coiyiriciice} 12) ?Nuisance Flooding? 'I'noreas'es- Across 'the- United. States -aces.5 necess- -iioers. -Tre'nrl Charleston. .SG 355 308 ?200 5:5 .3: Frenchmen Minor Tidal FIIOOd?iIiDa?s'N'e'arIi. "2.0.9 108 1880 1080 2000 2020 2040- 2080 .2080 2100 Figure ES. 8: Annual occurrences of tidal ?oods (days- per year}. also called sunny-clay or nuisance. flooding. have inoieasiio for 55515 U. 8. coastal. cities. The tigu're 555555 55155551 55555555555 {orange bars} {or two of the location's? Gha?eston. ISO andSanII Francisco {ISA?arid future proieotions through 2-188. The 55155555555 based upon the con- tinuation of the historical trend {blue} and under median at 5 and 8. 5 conditions. From Figure 12. 5. Chapter 12. 5. Assuming storm characteristics do not change sea level rise "will Increase the frequent}: and- extent of' extreme ?ooding associated with coastal. stories such' as; hurricanes. and. nor ?easteis I {very high confidence) A projected inore'ase in. the intensity of hurricanes? in the North Atlari- tiIcI {medium confidence) could increase the probability of extreme ?ooding along most of the U. Atlantic and Gulf coast states beyond what would be proieded' based solely on relative sea level Ir-iIseI. l-ioweverII there 15 low confidence' at the projected increase in frequency of' In- t'itnse Atlantic hurricanes, and the associate-d flood Irish amplification, and flood affects could be offset or amplified by. such factors: such as changes' in overall storm frequency or tracks (Ch. 12.: 5555155555 Circulation 5 The potEnti'al slowing .of' the Atlantic meridional overturning circulation (AMOC of which. the Gulf Stream is one componenty?as a result of' increasing ocean heat content and fresh- water?driven buoyancy changes?Could. have dramatic climate ieedbacks as the ocean .ab? sorbs less heat and CO5 from the atmosphere This slowing would also affect the climates of North America and Europe. Any slowing documented to date cannot be directly tied to hu- man?caused forcing primarily due to lack of 55555555 ObSerir'ational data and to challenges rt I't'histios .51 lunati- 555555515951 1 :i IlE?itEU?W?Sil?'i?iif? in modeling Mean, circulation changes, Under a higher scenario Show that the AMOC Weakenerover' the 215i century (few reryid?ice}. (Ch. 1-3} Regional-Ocean acidi?ea'tien . amenity mew nucleus; making-m more achil: [which with potential ml Imp-cu to" marine With. 13': Highetulatihade systems typically have a inWe'r buffering: capacity againat changing -ac_idity,_ exhibiting sooner 't'haniow-latitude systems..-The rate-of acid:? .ific-atien 'ia' unparalleled'injat ieaat'the past 66 millien years (medium con?dence), Under the higher scenario the globai average surface-ocean aciciit}r is pro?ted tO-increaee by- 100312 te con?dence), (Ch. 13] Acidification is regionally-greater'than the global average alongUS. coastal systems we result cit upwellingl'iega in the Pacific Northwest). (high con?dence}. changes in freshwater. in the (Juliet Mainei'?nedium and in urbanized eatuar'ies?iit'gh con?dence). (Ch. 13} Ocean Oxygen temperaturea, riaing .sealevele andchanging' patterns-of precipitation,_ winds, nutrients, and ocean circulatitin are-contributing to overall declining oxygen cent-em trat'iensjat'intiarmediate depths in various ocean. locations-and- in'man'y coastal areas. Over the-last hall-f centuryi major oxygen. losses have occurred. 'iniin'landr'eeas, eetueriea, and. in the coastaland open mean (high cen?eeiice)T Ocean eXygen levels are preiected to decrease-byes the higher-scenarie thy-21 [10 relative-to prei'ndiiatria'l valueeihigh ceii?dencr}; (Ch. 13] Ciimate Change in Alaska and Berber. {hermetic Continues 'teDutpace Global Climate Change- R'eaid'ente ef Alaskaare en- the'fran't lines of climatechengei crumbling-buildings, roads, and bridges and eroding shorelines are commonplace Acceie'rated meitin'g-zoimuitiyear Sea ice- covelijlmasa less tram-the GreeniandIceESheet, reduced snow-over, and pennafmet thawing are stark examples of thelrapidz-changee intent-ring in. the'Atc'tic,- Eartha-mere, because elementa- ef the ciimates-eyatem are interconnected {see Bea the Arctic in?uence climiate conditibns outside. the-Arctic. I 19- ?Zi?alfigge fiikac?l?iri 5: EREUIWE Summary I ?E?Iue'ciai Iii-rape?: Arctic Temperature Increases. With?! Rising Alaskan pennafrost temperatures are cau5iIrIgI permafrost to thaw and become more" discontInuous this process re1e55e5 additional carbon dioxide and methane re5ulting' In- aid-- ciitional warming (high con?dence}. The overali magnitude of the Ipennafrost?Ic-arbon feedback i5 uncertain (Ch. however, it is clear that these erni55ion5 have the potential to compromise the 555in to limit global termperature increase-5 (Ch 11) Ahnos'pheric circulation pattern5 connect; the climates of the Arctic and the contiguous Uniteo States Evidenced by recent racord warm temperatures .in the Arctic and emerging science; the. .midlatimde circulation has influenced observed arctic temperature5 and sea- ice [high 555 ?dence}. However, Confidence' IIs low regarding whether. or by what mechanisms obserVed I arctic warming may have in?uenced the midlatitude circulation and weather patterns over the continental United States; The influence of arctic changes on U. 3. weather over the- coming. decades remains an open question with. the potential for significant impact. {Ch 11) Artti'c Land. lee Loss Arctic land-tie 1555 observed in the'last-th'ree-decades continues, in some-cases accelerating- (oery high con?dence}. It is certain that Alaska glaciers have lost. mass over the last years,_ with each year since 1934 showing an annual average ice mass less than the previous year Over the satellite recorri average ice. mass loss From Greenland was ?269 Gt per year between April 2002 and April Z?i? seceleratin'g? In recent years (hIgh Con?dence) 11} 55555.5me Immuuaw,me mine mmamma?mue MW 5555555555. Arcticsea ice loss isexpec?tedto continue through the 21 st mammary-twig resulting in near.- ly sea ic5=iree=late5urnrri5rs by the IMGs-(eery higheon?draee). it- Is very likely that human activities have contributed to observed arctic surface temperature warming,- sea ice -1o55 _giacier ?mass loss,- and northern hemisphere snow. extent decline (high- con?dencc}. 11)- 5:55:15 Hafiilili?i {hit}. is: 32555555545: waterline? .20 PEI Ite i-r. 219 41:9,} fag-hat I Summary Muitiye'ar Sea tee He's Declined 'Dra'matiaaliy :15 3:9 2:5 '19 115 La 4.5 Staples?13.993 2.6% per-decade tare?mm mean 2:42 mieien sq; miles. me: 1995 1999 1995 29m: anus 20.19 2915' Vaar SeptemberSa'a lee-Extent 9.0 Figure ES. '19: September sea ice extent and age shown for {lap} 1994 and (-middle) 291B. illustrating significant re- 'duetione- in sea ice extent and age (thickness). The bar graph in the tower right of each pane! illustrates the 999 i419 area innit million kn?) covered within each age category {a 1 year}. and the green hare repreeant the. maximum extent for each age range during the retard The year -1934'Ie representative at September sea ice during the 19995 The years -1994 and. 2919 are selecmd as. endpoints in- the time series; a metrie tit-the aemptala time series is ?available at http: (rave. gafehasa, geuicgihinidetails. (batten) The satellite-era arctic sea tee; areal extent trend from 1919 to 2916 for September (unit- million mil}. Frinm Figure 11.1 iI'i'i Chapter 11' 21. 1-. Change11:99.93th Fang.- 013111 13:: 1112-1: ?rf-c-i Averaged Warming tori-2?C 13,6111 win-sequins Major lie-1111111111115 'in' Emissions Human activities are now- the dominant cause of the observed trends? 111 climate Ebr that reason, future climate prof-actions are based on scenarios of how human activities will continue to affect the climate over the remainder of this century and beyond {see Sidebar. Scenarios Used 111' this .Assessment).Tl1ere remains significant uncertainty about? future emissions due to changing. economic political-I and demographic factors For: that reason this report quantifies possible climate changes for a broad set of blausiblo fu'bJre scenarios through the end of the century.- {Ch 2- 4 10 14) 1111111 higher 11111111:th acres] [m high con?dence). in 2014 rates Millicent-wink growth mite carbon-1mm [medium mesm- Irina-swing 'trIend continuation", it is not yet iterate that tire gm average tempera-tree to Helium Web-111111 Gl'obal' mean atmospheric carbon-dioxide (C01) .concentra tion has now passed-100 ppm, a low at that-last occurred about-'a'rnillion years ago, when global: average were significantly higher than today (high con?dence}. Continued in .0132 emissions .overItbisI'century and beyond would .leadIto an atmospheric concentration not experienced in tonsof'rnillions-of years {medium con?dence). The 111111111111aria};r emissions rate ofI-nearl'y '10 (31C per year'suggests' that there, is-no climate analog for this-century an least the last 5.0 million (Ch. Warming and assbciated. ciimato-Effects from (ZOE-omissions persist 1111- deca'cles to millen- .nia..ln the neareterrn,.changes in climate are determined by past'and present greenhouse-gas emissions modified. by natural variability Reducing not emissions of is necessary to' limit .- near?term climate change and long-term teaming Other greenhouse gases to Ig., methane} and black carbon aerosols exert stronger 1We1'1'1111'1'g effects than CO: on 'a per ton basis. but they do not persist as "iong 111 the atmosphere {Ch therefore mitigation of non?C05. species contributes to nearrterm cooling benefits but cannot be relied upon for ultimate stabilization goa1s1I(IVery high con?dence} ((311.14) (Cleo. .14} Stabilizing global mean temperature to less than 3. above pteindustriai levels requires substantial reductions 111 not global C01 emissions prior to 2040 relative to presont-day values and likely requires rie'tI' emissions to become zero or possibly negatiire later 111 the contory After ac- counting for the temperature effects of non-CO species, cumulative global CO: emissions Irnust stay below, about 800 Gt?' 111 13113191" to pm?de a likelihood of proventir1g3. (20C) of lot; 11.1 Pianooal f- irritate: assassin-ans.11111111119 .1 22 fists: 5?:1 I warming. (listen estimated cumulative. emissions since 185?0 no more than approximately may be emitted in the future In order. to remain under this temperature limit.- Assuming. giobal emissions are equal to or greater. than those consistent with the RCP4. 5 scenario. this cumulative carbon threshold would beex'c-eeded In approximateiy: two decades.- (Ch. 1.4) Achieving global. greenhouse gas emissirins reductions before 2033:) consistent with targets- and actions. announced by gtiirem?mems in the lead up to the- 2015 .Pa'ris climate Conference would hoid open the possibility of. meeting the long-term temperature goal of limiting glob- a1 warming to a. above prein'dustriai levels! whereas there would be IiirtUail}! no chance if not global emissions followed a pathway. well above those impiied by sount'ry an- nouneements. Actions' the: announcements are, by themselves insufficient to meet a 3. EFF.- goal; the likelihood of achieving that depends strongly. on the magnitude of global amiss sions reductions. after 2030. (High cors?ticncr} (Ch. 14) I Climate intervention or geoenginee'ring Strategies web as selar radiation management are measures that attempt-to limit or reduce jglobal'tem perature increases. Furthersassessments: of the technital risks, coabenefitss and. governance challenges-oi climate intervention or are asyet necessary stepbefore ju'dgrnentsabout-the benefitsand risks ofi'these spproaches'can be made with high cmfid?ncELfl?Iigh con?dence) 14} i In recentderfades. land-Use changes have tome-cl .the' terrestrial biosphere. {Soil and plants) into a net "sink"? for carbon (draWihg-downcarbon from the atmosphere}, and this sink since 1980 (high .Betause-i'ot the uncertainty in the trajectory of land cover. the possibility ot-tlIeiand becoming a net carbon sourte cannot be excluded [any highcon?iieuce)?. Iii) - There is-a- Signi?cant Pessihility. for Unanticipated Changes effect on the Earth system, through-the fuels and widespread deforestation resulting release of carbon atriIosphere. .as Well .asfth'rough emissions of other greenhouSe..__gasessand ra'di'ativei'y active subtite'nceIi from human actiIritie's; is Unprecedented. ?l?here' is-s?ignificant potemial for humanity's effect on the planet-to. resuit?in unanticipated surprises and a broad consensusthat. the'hirther'andli'faster the. is pushed towards warming. the. greater; the risk. of sirch'-surprises. . There are- at'least two types of potentiai surprises: compound wants. where multiple extreme cii- more events occur simultaneously or- sequentially {treating greater ouerail impact] and critical. threshold or ripping. point events where some threshold is crossed in the climate system (that; leads to large. impacts) The probability of such surprisesesome of which may be abrupt and I or irreversible?as weii as other difficult-tormanage. impacts increases as the influence-of human activities-on the ciimate system increases. (Ch, 15'} 23. 2:51?, Fir-s enter- i'l?i'I'tsli slit- EXEEHIEVE science Spearmint-?soon Unanddpeted and dif?cult or WINEto?mnmgedunguin the-dilute system are possible ?ire-tam the unset-Isthmus Windmill!? masto- mm It Positive'feedbacks- (settereinforcing Cycles) within the climate system. have the potentiai to accelerate human-induced. climate change and even shift the Earth?s climate system in part: or in whole, into new; states that are very different from those experienced In the-- recent past {for example, ones with greatly diminished ice sheen or different large-scale patterns of mostphere. or- ocean circulation) Some feedbacks and potential state shifts can be modeled and quantified; others. can. be modeled or identified but not quantified; and some are probably still unknown (Very. high con?dence 111 the poteIItial- for state shifts and in the incompleteness of knowledge about feedbacks and potential state shifts) ((311.15) The physiCal and socioeconomic impacts of extreme events {such as Simultaneous heat and drought, wildfiies associated With hot and dry conditions or ?ooding associated with high precipitation on top of snow or waterlogged ground) can be greater than the sum of- the parts {nary high con?dencei Few analyses consider the spatial or temporal correlation henceen extreme Events (Ch 15) While climate models incorporate important climate processes that can be well quantified they do not include all of the processes that can contribute to feedbacks (Ch. 2), compound eit- treme events. and abrupt and or irreversible changes For this reason future changes outside the range projected by climate models. cannotbe ruled. out. (my high con?dence). Moreover, the systematic tendency of Climate models to underestimate temperature. change during warm paleoolimates suggests that climate models are more likely to underestimate than to overesti- mate the amount of- longrterm future change (medium con?dence); {Ch 15} Filly?!? Manna-rat Climate Meet-amen; ?t?tililjiilrc'l 24 Cans-ire rinse-re. triers-m hirer-r1! i Elictutlre Summaii'" Box E53: A Summary of Advances Since NEAS Advances in scienti?c-unIderstanding-and scientific-approach as well as developments inglobal policy. have occurred since it detaiied summary of these advanCes can be found at-the end ofChapte'r .1: Our-Glob- ally Changing..CIimat_e.IHighiights of what aspects are eitherespeciaiiy strengthened or are emerging In the. current ?ndings-inciude I Detection and haire been made-in the attribution-of the human in?uence for individual climateand weather extreme-event's since (Chapters 7.5.133- Ilhnosphenic circulation ond'errifrerne events: The extent to which atmospheric circuiation 'in'the midlati??, Itudes is changing. or is projected to change poss?ibiy' in ways not captured by current climate modeis.. Is a new important area of research {Chapters 5 5 2J. increased understanding of specific types. of extreme events: How climate change may affect speci?c types of extreme events In the United States? i5 another key area where scientific understanding has ad- vanced. (ChaptergJI High-resolu?an global donate model simuiotiaas: As computing resources have grown, multidecadai simplations of- global. cl rmate models are now being conducted at horizontal. resolutions on the order of 15 miles: {25. km) that provide more reaiistic characterization of intense weather systems, including hurricanes. {Chapters}, Oceoosoodoaostolmrs. Ocean acidlii cation. warming and oxygen loss are all? Increasing. and scienti?c understanding of the saverity of their impacts is growing Both oxygen loss- and acIclIi' cation may be mag- ni?ed in some US.- coastal waters. relative to the global average. raising the risk of serious ecoiagi'c'al and economic. consequences. (Chapters 2 'locoisea ieveichooge projections: For the ?rst time In the NCA process. sea level the projections incorpo- rate geographic variation based on factors stich- as local land subsidence. ocean currents. and changes in Earth?s gravitational iieid. [Cha pier 12}. Accelerated ice-sheaths: New observations from many different sources con?rm that ice?sheet loss vs accelerating. Combining observations with simultaneous advances in the physical understanding of ice sheets leads to. the conclusion that up to 8.5 feet of global Is'eIa ievel risers possible by 2100. undera higher scenario up from s. 6 feet' In [Chapter 12]. loosen?ice oreoierrtenr: The annual arctic sea ice extent minimum for 2016 relative to- the long-term re- cord was the second lowest on record The arctic sea ice minimums In 2014- and 2015 were also amongst the lowest on. record. Since 1981 the sea ice minimum has decreased by 13. 3% per decade morethan 46% over. the 35 years. The. annual arctic sea ice maximum in- March 231? .was the lowest maximirm areal extent on record {Chapter 1 11 Poten?oi surprises: Both largeeseale state shifts at the climate system (sometimes called "tipping pone") arid compound extremes have the potential to generate unanticipated climate surprises. The further the Earth system departs from historical c?mate forcings and the more the climate changes, the greater the . potentiai IrortheIse. surprises. .{ICIiiap'tIer 15). Mitigation: This report discusses. some important astec'ts of climate science that are relevant to long-term temperature goals. and different mitigation scenarios.r including those impiied by government. announce- .ments for the Paris Agreement. (Chapters 4 14). 25 '4 liaise-nit 11:; ?3 . ii .. ELM-trill}! aspen Con?dence Level . Likelihood .Htt'w Sims evidence metres . theory. multiplesotsotrs. consistent. 59%10039 results well documented and accepted memos sti: him seat-loos ?titan-hits)? mm very {_ritt'ti'f Morients es'idenee- {some sourc- 135. some mom methods -. very meter Mummies else-J. medium Frseer-10m Suggestive evidence {after soure- es. ?ddled considers?! Mime are Lr: Her aloe-comedies sotreolsof atrium ass-seer . ?Nil-Ethel} Imlusitrs strideme {lira-titted sounder Wuh' Inconsis- 056-3335. tent limit-ins. pour endles- Minds not tested slur}. or leek er opirtieris - were were err-rear. lJ'ttititts'y' 095-555.- {Ht?1% Con?dence levels and likelihood statements used in the Executive Summary. As'lan-esample. regarding 'likelyie 56.- probability ?can be interpreted as =3 likelihood digest-- er'than .2 out of statEmer-?tt to hosed-sin or truerltlot; all likelihoods are used in the. report. I I I ?utters ease-Emlyn??t?rjiuim: 26 I Thisdocurnen't responds to requirements of "Section 106 of the US. Global Change- iiesea?rch Act of 1995 (EL. 101 r605. It-d_ms not express any regulatory policies of-the United States .osanyof its agencies! or make any'?ndin'gs effectihat Could serve as predicatesof regulatory action. Agencies must comply with. required statutory and-regulatory processes before they could reiy- oneny statements inthefdocument or by the as basis for. regulatory. actio n. This document was preps red In. compliance with Section 5 1 5- of. the Treasury and General Gouerhme nt Appropri- - ations Act ?or Fiscal Year 2001 (P L. 1%554} and inforInatio'n quality guidelines issued by the Department of Com-- merce 1- National Oceanic and Atmospheric Administration pursuant to Section 515 cio. n'oaa. gow' htmi). For purpdses of compliance with Section 51 5 this document .Is deemed a ?highly in?uential scienti?c assessm enfiHlSA}. The report gra phics follow the 150 191 15 standard which includes the necessaryr information to achieve reproducibility. ._ln ail cases, permissions were'setured. bythe .5. Government to use andfor'ada pt copyrighted material contained in this document. High-resolution art is availabie at stienceZDI 2 globalc-hange .gov._ With accompanying captions providing soLIrce and credit information. . 32' C5 {ob ai an 9.6? Re. sea rch- 9ng r-a 1.55.180 (.3- NW Suite E3100 'Washing'ton, DC US Tab Summary Findings NCM summary- Findings Summary. Findings. These Summary Findings represents high?level o'l?the material-in the underlying report. 'The'findings eonsolidate- Key Messages-and. supportingevidenee from 16 national-level tepic cha?tersrio regiOnaichaptersr and 2 chapters that focus-on societal response strategies (mitigation and adaptation); Unless othenuisenoted, qualitative-statements regarding future eonditi'ons in itheseSum'n'iargi,r Findings are. broadly.'appiieable. across the range of different levels-of futurec'li'mate change and associated impacts-considered in this report. 3. Communities Climate change creates. new .risksand exacerbates. existing vulnerabilities.in-communities across- the United-States, presenting to human health-and safety-quality of life. and thereto of economic. aroma. climate Change are. already being felt: in communities across the country. More frequent; and. intense extreme weather a'nd climate-related events. .as?weii'as changes- "in airerage. climate -.eoneli_tions._ are _'expecte'd to continue to damage-infrastructure, ecosystems, and social systems; that provide easential bene elite Iii-communities. Futu re - climate change .is' expected-to further disrupt manyareas of life, exacerbatingexisting challenges-to pros?- pority pbs?d by aging and deteriorating infra.- structure?; stressed. ecosystems.- and economic inequality. Impacts-within and across-regions will not be distributed eQually. Peoele'arho'are already'vulnerable, including. lower?income and other marginalized lower capacity to prepare for antl'cop'c with Extreme weather and Climateerelated events and are ex- pected to- experience greater impaets. PriOritiz- ing?adaptation actitins for the most vuinerable' populations would contribute to a more. equi? table future within and aoroSs.conimunities. Global action insigni?cantly cut-greenhouse- g?asremissio'ns can substantialiyreduce cli- mate-related risks. and increase [opportunities for these. populations in the-longer term; Without substantial". and sustained? global mitigation and regional adaptation: efforts. climate change isex'pected to cause growing losses-to-American infras'trUcture and pressurised impede tiie- rate ofseconomic growth over this century. In the. absence of- signi?eant global mitigation action and regional adaptation efforts,' rising temperatures; sea. level rise. and changes in extra-me events are expected toin'rhreasingly disrupt and damage-critical 'infrastructure'anc'l property, labor vitality of our communities; Regional economies-and industries-that demandon natural resourcr esandffavorabie climate conditions. such as "ti [a?oat Change Rossetti: Program- ag?iculture', tourism. and fisheries, are vui'n'e'r- able..to'the- growing impacts of climate change. Rising temperatures a re projected to reduce the effici'e ncy. of creasingenergy-demands, resulting in higher e?lect?riciti,r costs. The impacts of?ciimate change beyond ourborders are expected to increas- ingly affect our trade and _econorny,r-ineiuding import, andexport prices. and U.S. businease?s in; um t-ia't Ioriai {ii-snare its sass-iron a with overseas operations and supply Chains. Some aspects of our economy may see slight near?te'rm 'improtrem'entsJin a'm'odestly. warmer worid. 'H?wever. the centinuetl warmingithat is projected to colour without substantial and sustained reductions in global greenhouse gas. emissions is e?icpect?ed?to cause: substantiai net damage to met-.143. economy throughout this SummaryFindings century. especially. "inl'the absence of?increa'sed- adaptation efforts.- With continued growth-in emissions at historic rates. annuai'lo'sses in some economic. seCtors are projetted to reach. "hundredsof billions-oi dollars lay-the end of the centuryumoi'e than the .currentgross' domestic: product (GDP) of many US. states. 3. Interconnected Impacts Climate change affects the natural. built-and sociai systems we rely- on individually: and through their-connections .to one another. These interconnected systems are increasingly VUlnerahle to cascading impacts that are-often difficult to predict. threatening essential services within and beyond the Nation's Climate-change presents added risks to inter- are alts-soy exposed aging. 'and de? ?te?iorating infrastructure, land-use Changes, and p?opuiation growth. Extreme-weather. and, Climate-related impacts-on one system- can re? sultin increasedrisks-'or'faiiures. in other crit- ical Water resources. food productiion and distribution. energy-and trans- trade, and national security. Thefull extent of; climate change.- risks to _i_ntert:onnected systems. many. of- regional and national boundaries. is oftEn'greaterthan-the sum of risks to.- individe us]= sector's. Failure to anticipate interconnected Simplest-s canrlead to missed opportunities for effectively managing. the risks-oF-ciimate change and canalso lead to management responses thatincrease risks to other sectors and regions. Joint planning with stakehoiders aeros's'se'cu' tors. regions. and risdictions .can-heip; identify- crit'ical risks arising from interaction among systems aheadioi' time. 4.. Actions-to Reduce Risks: Communities. gotternments, and businesses ateWotking?to rediice risks tram-and costs asses elated with cl irnateichange-by takinga'eti'c'n to lower greenhoUse gas. emissions. and. implement: adaptation strategies. while Mitigation and adaptation efforts have expanded substantially-in- the?last four years. they do not yet approach the scale considered necessary? to a?Voidsubstantial damages human health- oser the coming decades. Future, risks from climate change depend primarily on decisions made-today. The inte~ gration of-zclimater'rislt into-decision-making' and the implementation-of adaptation activities- hatic. significantly increased since'the Third. NationalICiirnate assessment in.-2014. including F's'trgisit?l. 126 in areas'of financial risk reporting, capital in? vestmentplan'ning. development ofen'gi'netering planning. and di_Sas'ter- riSk management.Transformations in-the Ener- the displacementef coal by nature! gas and-increased: deploymem of Four-1 i1 anon-1 Til-lamina? {is asses ant. renewable energy?alon'gw'ith policy actions at the irrational, regional, stately-and local lev-' els are reducing greenhouse gas emissions-in. the United States. While these adaptation and mitigation measures can help reduce damages in a number of seetors; this assessment snows that; more-immediate and substantial global. greenhouse gas emissions reductions'ias well as regional adaptation.elforts, would beneedEd to"- ?Summary Findings acid the most severe conlseqnences in the-long term. Mitigation and adaptation actions also prose ntto'ppo rtunitie's. for additional benefits that-are often more immediate. and localized, such as improving local air qualityand econ- .Omies'through investmentsin infrastructure. some benefits. such as restoring: ecosystems and increasing-community vitality, may be harder "to" quantify. The q_'uality_janid'quantity of water available-forties by. peppie. arid-ecosystems across thecountry are being affected by climate change; increasing risks and costs tat-agriculture. energy production. recreationi and the environments. Rising-ai'rand water temperatures and chang? esin precipitation are intensifying droughts. increa sin'g- heavy downpoUrsg reducing-snow? pack. and causing declines-in surface water quality. with canying'impaots across regions. Future-warmingrw'iil add to the stression water suppiiesand adverse!)' impact the availability of Water 'of?th?e United States. Changes- insthe. relative-amounts-and timingof snowand rainfall are leading?to mismatches between-war- 'ter availability and needs-in- someregions, pos- ing- threats to. for example; the future reliability.- of'hydropower production. in the Southwest and the Northwest. Groundwater depletion is exacerbating drought riskin. many parts of the - United States. particularly'inthe Southwest and Southern Great Plains. Dependableand safe. water supplies-for Caribbean. Hawaii, and Island communities are threatened by, drought. flooding and saltwater contamination dueto sealevel rise. Most. 1.1.8.. power plants rely on a steady supply of water for cooling? and operations are expected-tube affected'by changes in water availability and temperature increases. Aging and deteriorating water infrastrucmre', typically designed for past. environmental conditions. compounds the, cli-' mate-risklaced by society. watermanagement strategies-that account. for-eh'ang'ing-climate conditions can help rodnce present and future risks to water scour-i but implementation of imprints-from climate change-on extreme?weath'er and quality. and the transmission insects food. and water increasingly threaten the health 'snd-WelI-beingof the American people,- particularlypopuisti'onsthat Changes in temperature and, precipitation are increasing air Quality and health Wildfire and ground-less] ozone. pollution. Rising-air and water-temperatures and more us. {transition-H?s Research 'ngram -inte'nse- 'extrEme-events are expected to crease exposure to waterborne and foodborne disease-a. affe?ting-food and water'safety; With no ntinued warming. cold-related death?s-arc. F't?nu'tl'i projected to deerease-soonest-Creamed deaths are projected to'in'crease; in- most regions. incre'aSes in heat-related deaths are expected ?to outpace reductions In cold-related deaths. The frequency. and Severity of allergic ille- nasces. 'inciudingo-asthma and hay fever. are expected to increase as a result cf a changing climate. Climate change? Is also projected to alter the geographic tang?? and distribution of disease-carryinginsectsand 'pests..e11posing- more people. to ticks that disease and mosquitoes thattransmit viruses such- as .Zika. West Nile. and-dengue. with varying iinpacts'a'cros's region's. Communities in the- Southeast. fur example. are particularly-vul- nera'ble to the combined healthimpacts from indigenous Peoples discuss. heat. and ?ooding, Ere trem'e weather and climate-related events-can 'havelas?tin'g mental health consequences i'n'a'f- 'fected communities. particularly if they result in degradation of livelihoods or community relocation. Populations including- older. adults. children. low- ~income communities. and some communities .ofcol'or are often disproporr. tionately affected by. andiessresilient to. the health impacts of climate change, Adaptation Iand mitigation policies and programs that help individuals, communities-and states prepare for-the 'riSksof a: changing-climate redu?ce'the' number-of injuries, illnesses. and'cleaths from climate?related health outCornes. Climate-change increasingly threatens Indigenous communities livelihoods. economies. health, and 111111111111, identities by disrupting interconnected social. Iphysical._.and' ecological .svtitem's. Many Indigenous peoples are reliant on nat? ural resourcesfor their economic. cultural, and physical well-being and are often unique?- .ly affected by climate change. The impacts of cliinate-cha'nge-on water, 11111-11. coasta_l_:areas. and} other natural resources: as well as infra- striicture and: related- 11111111141115, are expected to increasingly disrupt indigenous peoples' liveli? hoods and economies including agriculture and agtofcrestry. i" slung. recreation. and tourism Adverse? impacts on subsistence activities have?. already-been observed. Its-climate changes con- tinue-arise rse' impacts culturally significant species and resources. are expected to result in negativeIphySicai and mental health effects. Throughout the United-States climate-related - {Slohai 11111111111 Basra: ell-Fitters ?11 impacts are causing'scme lntiigenotu peoples to consider creatively pursue community 'rIc- location as an adaptation Strategy. presenting challenges associated iwith maintaining. cultural and community continuity While economic. political and infrastructure limitations may affect these communities alirility'r to adapt-- knit social and cultural networks present opportunities to build community capacity and increase resilience. Many. indigenous peoples are taking steps. to adapt to climate. change impacts structured around self-determination and traditional knowledge. and some tribes-are pursuing mitigation aetic'nc through develop- mentiof renewable energy-on tribal lands. F1111111111'111111r11111 Ijniatr? 1?11: wheel 8. Ecosystems and Ecosystem Services Summary Findings- Ecosystems and the benefits they provide to isoCiety are being altered by climate change and these impacts are prioiected to continue. WithoLIt substantial and sustained reductions" In global greenhouse gas emissions, transformative impacts on some ecosystems will Occur: seine corai reef. and sea ice ecosystems are already. experiencing sueh transformational changes. Many be'nefitsprovided by ecosystems and the environment. such-as clean air and ?water. pro? tection from coastal ?ooding-,Iwood and fiber; .cro'p pollinationi'hunting and fishing. tau rierrI, cultural ider'itities; and more will continueto be degraded bythe impacts. of climate change. increasing changes in insect and disease outbreaks. and other .stressors are' expected to decrease the ability. of US. for- ests t'o support-Eonomic and. subsistence aetitr?ities'. Climate change-has already'had- observable impacts on bicdiversit-yi ecosystems and the benefits they provide to society. These. impacts include the. migration of native species to new areas and the spread oi? Invasive species. Such changes are project? ed to continue and without. substantial and sustained reductions In, global greenhouse gas emissions, extinctions and transformative- 9.. Agriculture and Food impactson cannot-be avoid- ed in the long term. aspectsof regional heritage'an'd quality of life tiedto ecosystems outdoor recreation willchange. with the climate-and as a result.I future} gener- ations can-expect. to experienceand interact with the naturai'environinent in ways that are. different from today, Adaptation strategies, including- preseribed burning; to reduce fuel _for wildfire; creation of safe- havens-for important species. and control of 'invaSive being implemented to address ernerging-irn-i pactsol" climate targeted response-actions are u?ndervvay. many impacts, including losses of unique coral reef andsea. ice ecosystems; can only tie-avoided 'b3_.significant? 1y reducing giobal. emissions of Carbon dioxide. and other greenhouse gases. Rising temperatures. extreme heat-droughts, wildfire on rangeiands. andhe'avy downpours are expeCIed to increasingiy- disrupt agricultural prodtIctitrity in the United States, Expected immac- es to firestockheaith. declines in crop-yieids andqualitv, and changIes'in extreme 'eiie'nts in the United States- and-abroad threaten rural security, and price stability. Climate change presents numerous challenges to sustaining and enhancing crop ptoduetittityi livestock heaith and the economic vitality of rural communities. While. some regionsi'such as the Northern Great Plains) mayI see con* ditions conducive to expanded or. alternative crop productivity over the next few decades overs]: yields from major crops are expeCt- ed to decline as a consequencerof Increases in lie Change Research Program temperatures'and possibly- changes in water availability. soii'erosion. and disease and pest outbreaks; Increases in-temperature's daring- the groWingIseascn in the .Midvvest are-pro- jected th'e'largest: contributing factor to declines in the. productivity. of US. agriculture. Projected'increases in extreme heat-conditions. are expected to lead'to. further heatst'ress for livestock, which can result .inlarge economic Assessors:- losses for producers Climate change isalso eav- peeted to lead to large-scale shifts in the avail- ability and prises of many agricultural products across the world. with corresponding impacts on a'gr?iculttual producers and the (3.3., economy, These changes. threaten future'gains' in commodity crop production and put rural livelihoods at risk. Numerous adaptation strate- gies- are available to cope with adverse impacts Summary Findings 'of climate. variability and changeon agricultural production. These include altering what is pro- duced modifying the inputs used for'produc.- t',idn adopting new technologies and adjusting management Strategies. However. these strat- .eg'i'ea. have litrIit's under severe climate change impacts and would require sufficient long- and short-term investment in changing. practices. Our Nation' aging and deteriorating infrastructure Is farther stressed Iby increases in heavy pre- cipitation eventsi coastal flooding. heat. wildfires, and other extreme events. as well as changes- . to average precipitation and temperature. Without adaptation climate change will continue to de- iIin-aIdeI infrastructure performance overthe rest of the century ivith the. potential for cascading' Im- pacts that threaten oureconomy, national security. essential services._ and health and weli~beingI Climate change and extreme-Weather'event's are expected-to increasingly disrupt our Na- tion? energy and transportation systems. threatening more fragment and longer-lasting power outages, fuel shortages, and service dismptions; ivith cascading impacts'on nth-.- er? critical sectors?. Infrastructure currently? designed' for'historical climate conditions is more-vulnerable tofutureiweather extremes and climate changeji?he continued increase-in the frer'Iue'ncy and extentsf high?tide flooding due to _.sea level rise threatens .Anterica'sltril- I lion-dollar coastal propertyr market and public infrastructure. With cascading impacts to the. larger economy. In Alaska; rising temperatures. and erosion-are causing damage til-buildings and coastal infrastrucwre that will be costly to repair or replace, particularly in rural areas: the'seimpacts-are expected 'to- grow without till, _Eilohal Change Research Program adaptation. Expected increases in-the severity. and frequency tit-heavy p'recipitation'esents will affect inland in'i?rastr'IIctureIin every region, including access to roads. the viability. of bridge es and the safety of pipelines. Flooding: frets heavy rainfall storm surge and rising high tides. Is expected to compound existing issues with aging'finfraStructuIre in the Northeast. Increased drought-risk will threaten oil. and gas drilling and. refining. as well as electricity generation from power plants-that rely on surfacewater for cooling. Forward-lookinginfrastructure design, planning. and. operational measures and standards can redudc exposure and vulnerabil- ity to the lmpactsof?elimatechange and reduce energy use while 'providingjadditional near- -term benefits, including reductions in green- house gas emissions. National Climate assessment Oceans and-Coasts Seminary Findings" Coastal communities and the ecosystems that support them'are increasingly threatened by the impacts. of climate _ch?ange Without significant reductions In global greenhouse gas. emissions and regional. adaptation meesuresj. many eoastal regions will be transformed by the latter part of this century, with impacts affecting other. regions and. sectors. Even.? a future. with lower green- house. gas emissions many communities are expected to suffer ?nancial impacts as chronic high-tide. flooding leads to higher costs. and. lower property -.va.lues Rising-water temperatures,.ocean ?acidification, retreating'arctic sea ice, sea level rise, highrtide flooding; coastal erosion, higher storm .?surgc, andheavier precipitation events threaten our oceans'and coasts. These effects are" projected to-continu'e putting odeanand marine-'species' at risk, decreasing the productivity of certain fisheries, and threatening communities that rely on marine-"ecosystems for livelihoods and recreation,. with particular-impacts on fishing communities inHawai?i and the . Pacific islands, that-J3. Caribbean, and'the-Gulf. of. Mexico.- Lasting damage to coastal property. and infrastructure driven by sea level rise and storm serge is expected to lead to "financial and eommue nities?t with the Atlantic and Gulf: Coasts facing above-average. risks impacts on. coastal energy and transportation infrastructtire driven by sea level rise and storm surge have the potential 12. Tourism and Recreation for cascading costs and disruptions across the country. Even if signi?caht- emissions reduc- tionsoccur, many of the effects from sealevel rise- over particularly- through mid?eentury?are already-locked indue to his.- and many communities are already dealing with theemseouences, Actions to plan for and adapt to more frequent, iride- spread, and severe coastali?loodi?ng, such-as shoreline protection and conservation 'of'c'oast- alecosystems. fwould decrease direct losses and cascading impacts; on eth'e'r'sectors and parts _ofithe'countrye More "than half of the da mages to coastal property are estimated to be avoid- ablethrough well-Itimed adaptation measures: Substantial and'stistained reductions in global --greenhouse gas emissions wodld also signifie- cantly red'Uce- projected risks to fisheries-and communities that rely on them. . Outdoor recreation-tourist economies, and quality of life are reliant on; benefits provided byiour natural environment tha't?will lie-degraded by the impacts of ciimate' change in many Ways. Climate change poses risks. to; Seasonal and outdoor. economics-in communities across the United States, including impacts on economics centered around ceral reef-based recreation, winter reoreation, rand inland water-based recreation. - this affects-the well ?being oil-the people'who make their living Supperting these-seconomies, including and IndigenoIIs-communities. Projected increases Research-Program Smoke eventszare expected to. impair- outdoor recreational aetivities and visibility in wilderness-areas; Declines in show and ice cover caused by Warnier winter temperatures are-.eitpected to negativer impact the winter recreation-industry in the Northwest, North; 'ern Great Plain-,5 and the Northeast. Some - fish, birds, and mammals are expected to shift Where they live as a result; of climate change; ?lime?ts 'Su__mmary Findings with implications for hunting. ?shing-and other based around hiatorioei :use-oi'and? interaction 'wildlife? related aetivities. These and other cli- with or naturai resources in manyiareaa: mate-related impacts are expected to result in are at risk-Proactive: management strategies. deereased touriarn revenue in some places, and-_ such as the-use of projected stream tempera- for some communities ioss of identity. Whiie :tures to setpriorit?i'es for fisheonsenration, can some new opportunities may. emerge from help reduce'diaruptiona to tourist-Economies these ecosystem changes;- coitu'r'al identities and recreation. and eeo'nornie and recreational opportunities Glnha'i Program 32 (:iimate envision-m- 1' 112:;de 2mm. y?a?nxg?n; - - HIHIE 1er TH it: 1 IDE THREAT ASSESSMENT OF THE US COMMUNITY Daniel R. Coats L't-i 1131:.) Semie Seieci on Environment Change Global- communicate! and ecological: degradation, as well as same- change, are likely tc?tel competition for retainers, economic distress, endemic! discontent through 2019 and Mood Climate hazards such as extreme weather, higher. temperames, droughts, ?oods?, wild?res, storms, sea level rise, soil . degradation, and acidifying oceans are intensifying, threatening infrastrucnire, health and water and food se'ciirity. Irreversible. damage to ecosystems and habitats will undermine the economic bene?ts they provide, worsened. by air, soil,- water, and marine po?ution Eritreme weather events, many worsened by accelerating'sea level rise, will particularly affect urban. coastal areas in South Asia; Southeast Asia and the Western Hemisphere Dmage to communication,- energy?, and naiispoita?on infrastructure could affect. low-lying military bases, in?ict coonomic costs, and cause human displacement and loss of life Changes in the frequency and variability of heat waves, droughts, and ?oodse?eotnhii?ied with poor; governance practices?are: increasing water and food insecurity around the worid, increasing the risk of social unrest, migration, and' interstate tension in countries such as Egypt, "Ethiopia,1raq,. and Jordan. - Diminishing Arctic sea ice- may increase competition?particularly with Russia and China-w over access Ito sea routes and natural resources. Nonetheless, Arctic starts have maintained mostly positive cooperation in the region through the Arctic Council and other. multilateral mechanisms, a trend we do not expect to. change' in the near term. Warmer temperatures and diminishing sea. ice are reducing the high cost and. risks of some cominercial activities and are attracting new players to the resource-rich -region._ In 201,3 the minimum sea ice extent in the Arctic was 25 percent below the 30-year- average from 1930 to ROM 23