Coastal Flood Risk in Connecticut James O’Donnell Connecticut Institute for Resilience and Climate Adaptation and Department of Marine Sciences University of Connecticut NOAA Technical Report OAR CPO-1 GLOBAL SEA LEVEL RISE SCENARIOS FOR THE UNITED STATES NATIONAL CLIMATE ASSESSMENT Climate Program Of?ce (CPO) Silver Spring, MD Global Mean SLR Scenarios We have very high con?dence in 10 chance) that global mean sea level Will rise at least 0.2 meters (8 inches) and no more than 2.0 meters (6.6 feet) by 2100. 200 Highest - 2.0 rn Observed Scenarios 160 -- 120 -- IntermedialaLHigh 1.2 80 Intermediate-Low - 0.5 Lowest - 01900 1950 2000 2050 2100 Year Global Mean Sea Level Rise (cm above 1992} Figure ES 1. Global mean sea level rise scenarios. Present Mean Sea Level (MSL) for the US coasts is determined from the National Tidal Datum Epoch (NTDE) provided by NTDE is calculated using tide gauge observations from 1983 2001.Therefore, we use 1992, the mid?point of the NTDE, as a starting point for the projected curves.The Intermediate? High Scenario is an average ofthe high end of ranges ofglobal mean SLR reported by several studies using semi-empirical approaches.The Intermediate Lovv Scenario is the global mean SLR projection from the IPCC AR4 at the 95% con?dence interval. Charge In the Memorandum of Understanding between the Connecticut Department of Energy and Environmental Protection and the University of Connecticut establishing CIRCA included the direction that the institute should: Develop a predictive tool(s) for municipalities that accounts for local conditions and establishes a mechanism for determining appropriate planning based on the sea level change scenarios published by the National Oceanic and Atmospheric Administration in Technical Report OAR CPO-1. Conduct at least one statewide workshop and provide online access to such tool(s). Intermediate Low In IPCC AR4 scenario A2 the continued emission of GHGs was expected to lead to a concentration of 870 PPM by 2100 (more than twice the 2016 level) and a warming of the global average surface air temperature of 3.5 C between 2000 and 2100 (IPCC, 2007). The 5-95% range of the predicted rise in global mean sea level between the decades 1980 to 1999 and 2090 to 2099 was 0.23 to 0.51 m (or 0.75 to 1.67 ft). Updates • • • • Review of Observations in CT up to 2016 Review of IPCC (2013) Model Predictions near CT Model of Mean Sea Level variations in LIS Summary New Haven Boston noya'd Firming en ce Block Island share Island Gardiners Island, ?6?9 [Jet-?310. NOAH: US. Navy: NGA, GEBCD 2011(3mgle Europa Technoiogies 156 ft Connecticut Institute for Resilience and Climate Adaptation New Lnndun: (amidecade) 0.25086 (infclecade) 3 Detrended Nontidal ?uctations 2-5 Average 2 - 1 Sea Level C) U1 _2 1940 1950 1960 1970 1980 1990 2000 2010 Mean Sea Level I I ?Bridgepert I I 0'8 [115 New Lenden I I WilletePeint I I - I I -[0.?0.05 n' 43-U-?04 I I ?015-?06 4:1936 1946 1956 1966 19?6 1986 1996 2006 2016 ?121.! CIRCA Connecticut Institute for Resilience and Climate Adaptation 1880s, 1910s, 1960s Church and White, 2011 • The number and distribution of sea-level records available for the reconstruction. a The number of locations for the globe and the northern and 1930s southern hemispheres. b–f indicate the distribution of gauges in the 1880s, 1910s, 1930s, 1960s and 1990s. The locations indicated have at least 60 months of data in the decade and the number of records are indicated in brackets 1990s Church and White (2011) estimated the rate of sea level increase between 1900 and 2009 as 1.7 ± 0.2 mm/yr and 1.9 ± 0.4 mm/yr from 1961 to 2009 1.6 mm/yr 2.5 mm/yr LIS Sea Level trends are in-line with the estimates of GMSL Rise when VLM (0.7mm/yr) is taken into account. The most recent 15 years has been above the long term mean. The rate is equivalent to 4 mm/yr in LIS. Summary of Results Year 2020 2030 2040 2050 2070 2080 2090 2100 Mean (m) 0.15 Upper 95% (m) 0.25 NOAA (m) 0.06 Mean (ft) 0.5 Upper 95% (ft) 0.81 NOAA (ft) 0.21 0.19 0.29 0.08 0.63 0.96 0.27 0.23 0.34 0.10 0.76 1.11 0.32 0.27 0.39 0.12 0.89 1.27 0.38 0.31 0.43 0.13 1.02 1.42 0.43 0.35 0.48 0.15 1.15 1.58 0.49 0.39 0.53 0.17 1.29 1.74 0.55 0.43 0.58 0.18 1.42 1.9 0.60 l2 Climatic Change (2011) 109:5?31 Table 2 Overview of representative concentration pathways (RCPs) Descriptiona Publication?1A Model RCP8.5 Rising radiative forcing pathway leading (Riahi ct a1. to 8.5 W/m2 (~1370 C02 eq) by 2100. RCP6 Stabilization without overshoot pathway (Fujino ct a1. 2006; Hijioka ct al. to 6 W/m2 (~850 C02 eq) at stabilization after 2100 RCP4.5 Stabilization without overshoot pathway to (Clarke et al. 2007; Smith and Wiglcy 2006; 4.5 W/m2 (~650 C02 eq) at Wise et a1. stabilization after 2100 RCP2.6 Peak in radiative forcing at ~3 W/m2 (Van Vuuren et a1., 2007a; van Vuuren ct a1. (~490 C02 eq) before 2100 and then decline (the selected pathway declines to 2.6 W/m2 by 2100). a Approximate radiative forcing levels were de?ned as of the stated level in W/m2 relative to pre?industrial levels. Radiative forcing values include the net effect of all anthropogenic GHGs and other forcing agents Total CO2 Emissions (GtC/year) I 2050 2100 Year Figure Future greenhouse gas scenarios range from aggressive reductions to large increases in greenhouse gas emissions. The figure shows annual total C03 emissions in Gigatons of Carbon Though not the only greenhouse gas, CO: emissions are the dominant driver of global warming. The old greenhouse gas scenarios (dashed lines) have close analogs in the new scenarios (solid lines) similar scenarios are plotted using similar colors. Actual emissions for 1990-2010 are shown in grey. Year-to-year emissions of greenhouse gases, shown in this graph, accumulate in the atmosphere, causing C03 concentrations to rise, as shown in Figure 3-2. Scenarios with higher emissions cause atmospheric concentrations to rise rapidly, while lower scenarios cause concentrations to rise more slowly or decline. Figure source: Climate Impacts Group. based on data used in 2007 and IPC 2013 and Sea Level change by 2100 in from IPCC (2013) 180? 0.4 0.35 Change in mean MSL at 2100 in RCP 4.5 0.3 0.25 0.2 0.15 0.1 0.05 Figure 12. Sea level projection from IPCC (2013) for RCP 4.5 at the cell shown by the green cell in Figure 11 with the rate of vertical land motion added are shown by the solid black line. The 5 to 95% confidence interval is represented by the grey stripe. On the right of the figure the average sea level, and 5 to 95% range, for the interval 2090 and 2100 is shown for the 4 RCPs in IPCC (2013). - SNE is on High side of all intervals - SNE has larger variance than the global mean Sea Level Change Sea Level Change RPCZ .6 SNE Global Mean F353 F3 7* c: hJ-h OJCD ?sro -0.2 . 2000 20 20 2040 2060 2080 2100 RPCB SNE Global Mean 9?53 F3 F3 7* c3 kJ-b oath ?sro '-0.2 2000 20 20 2040 2060 2080 2100 RPC4 .5 SNE Global Mean 1.2- (18' (16' 04-* (12? (ft) 0 . -0.2 2000 20 RPC8 20 2040 2060 2080 2100 1.2' 1, (18' (16- 04-' (12' 0. .5 SNE 8: Global Mean 4 (ft) -0.2 2000 20 20 2040 2060 2080 2100 Figure 1. Sea level rise projections for Connecticut based on local tide gage observations (blue), the IPCC (2013) RPC 4.5 model simulations near Long Island Sound (yellow line), the semi-empirical model predictions are in orange and the magenta shows the ice mass balance projections. Caution Threshold Planning threshold Summary • CT is special (location and oceanography, weather, geology). Consequently, • We will get more SLR than other areas, and the predictions have prediction intervals. • We should plan for 50 cm (almost 2 ft) increase by 2050 and alert people that in the future higher thresholds may be required. • The increase in the area impacted will not be very large because of the geology of CT. • We should institute a decadal review and update to ensure new science is incorporated in the planning to minimize costs and maximize safety. • Since the coastal areas are flat small increases in MSL will cause a large increase in flood risk. The geometry and orientation of the Sound causes tides and surge to be larger in the west of CT so the impact of SLR on the flood risk is higher in the east. Zbur?: Est]. BaeE?faJ E?r?g'ialr Banyan-shits; BB. UEDA. JEN. amd'ih; 913 Use: 99mm? - ye. Ea i'E-ta E?s-graphics. I Araceli-THEFr. 'J?Sl?ra. H. and the FIE: [lit?I Samuunh I: I RCA Connecticut Institute for Resilience and Climate Adaptation