SW-NCA-color-FINALweb

Future Climate: Projected Average 105are shown in Figure 6.1. The three periods show successively higher temperatures thanthe model-simulated historical mean for 1971–2000. Spatial variations are relativelysmall, especially for the low-emissions scenario. Changes along the coastal zone are noticeablysmaller than inland areas (see also Cayan et al. 2009; Pierce et al. 2012). Also,the warming tends to be slightly greater in the north, especially in the states of Nevada,Utah, and Colorado. Warming increases over time, and also increases between thehigh- and low-emissions scenarios for each respective period as shown in the thirty-yearearly-, mid-, and late-twenty-first century plots in Figure 6.2 for the aggregated six-stateregion that defines the Southwest. Figure 6.3 shows the mean seasonal changes for eachfuture time period for the high-emissions scenario, averaged over the entire Southwestregion for fifteen CMIP3 models. For the low-emissions scenario, the amount of annualwarming ranges between 1°F and 3°F (0.6°C to 1.7°C) for the period, 2021–2050; over 1°FFigure 6.1 Projected temperaturechanges for the high (A2) andlow (B1) GHG emission scenariomodels. Annual temperature change( o F) from historical (1971–2000) forearly- (2021–2050; top), mid- (2041–2070; middle) and late- (2070–2099;bottom) twenty-first century periods.Results are the average of thesixteen statistically downscaledCMIP3 climate models. Source:Nakicenovic and Swart (2000),Mearns et al. (2009).