Future Climate: Projected Average interprets computer-model simulations of future climate in the region—what the patterns might be over the coming century for temperature, precipitation, atmospheric circulation (long-term weather), and hydrologic (water-related) conditions, such as snow water equivalent, soil moisture, and runoff for the Colorado River and in other basins.
Citation:
Cayan, D., M. Tyree, K. E. Kunkel, C. Castro, A. Gershunov, J. Barsugli, A. J. Ray, J. Overpeck, M. Anderson, J. Russell, B. Rajagopalan, I. Rangwala, and P. Duffy. 2013. “Future Climate: Projected Average.” In Assessment of Climate Change in the Southwest United States: A Report Prepared for the National Climate Assessment, edited by G. Garfin, A. Jardine, R. Merideth, M. Black, and S. LeRoy, 101–125. A report by the Southwest Climate Alliance. Washington, DC: Island Press.
Dan Cayan (Scripps Institution of Oceanography, University of California, San Diego and U.S. Geological Survey)
Mary Tyree (Scripps Institution of Oceanography, University of California, San Diego)
Kenneth E. Kunkel (NOAA Cooperative Institute for Climate and Satellites, North Carolina State University and National Climate Data Center)
Chris Castro (University of Arizona)
Alexander Gershunov (Scripps Institution of Oceanography, University of California, San Diego)
Joseph Barsugli (University of Colorado, Boulder, CIRES)
Andrea J. Ray (NOAA)
Jonathan Overpeck (University of Arizona)
Michael Anderson (California Department of Water Resources)
Joellen Russell (University of Arizona)
Balaji Rajagopalan (University of Colorado)
Imtiaz Rangwala (University of Colorado, CIRES)
Phil Duffy (Lawrence Livermore National Laboratory)
Key Findings
Temperatures in the Southwest will rise substantially (by at least 3°F—and up to 9°F—over recent historical averages) over the 21st century.
Climate models project reduced Southwest mountain snowpack during springtime for the rest of this century, mostly due to warmer temperatures.
Substantial parts of the Southwest region will experience reductions in runoff and streamflow from the middle to the end of the 21st century.
Climate projections show that the Southwest will remain susceptible to unusually wet spells but will experience occasional drought episodes.
Models project lower precipitation in the southern part of the Southwest and little change or increased precipitation in the northern part.
Figure Gallery
Figure 6.1: Projected temperature changes for the high (A2) and low (B1) GHG emission scenario models. Annual temperature change (oF) from historical (1971–2000) for early- (2021–2050; top), mid- (2041– 2070; middle) and late- (2070–2099; bottom) twenty-first century periods. Results are the average of the sixteen statistically downscaled CMIP3 climate models. Source: Nakicenovic and Swart (2000), Mearns et al. (2009).
Figure 6.2: Mean annual temperature changes (°F; left) and precipitation changes (%; right) for early-, mid- and late-twenty-first-century time periods. Temperature changes and precipitation changes are with respect to the simulations’ reference period of 1971–2000 for 15 CMIP3 models, averaged over the entire Southwest region for the high (A2) and low (B1) emissions scenarios. Also shown are results for the NARCCAP simulations for 2041–2070 and the four GCMs used in the NARCCAP experiment (A2 only). The small plus signs are values for each individual model and the circles depict the overall means. Source: Nakicenovic and Swart (2000), Mearns et al. (2009).
Figure 6.3: Projected change in average seasonal temperatures (°F, left) and precipitation (% change, right) for the Southwest region for the high-emissions (A2) scenario. A fifteen-model average of mean seasonal temperature and precipitation changes for early-, mid-, and late-twenty-first century with respect to the simulations’ reference period of 1971–2000. Changes in precipitation also show the averaged 2041–2070 NARCCAP four global climate model simulations. The seasons are December–February (winter), March–May (spring), June–August (summer), and September–November (fall). Plus signs are projected values for each individual model and circles depict overall means. Source: Mearns et al. (2009).
Figure 6.4: January (left) and July (right) BCSD average temperature for California (top), the Great Basin (middle), and Colorado (bottom). The maps show the three regions over which the temperatures were averaged. Source: Bias Corrected and Downscaled World Climate Research Programme's CMIP3 Climate Projections archive at http://gdo-dcp.ucllnl.org/ downscaled_cmip3_projections/#Projections:%20Complete%20Archives.
Figure 6.5: ARCCAP multimodel mean change in the length of the freeze-free season between 2041–2070 and 1971–2000 (top) and simulated NARCCAP climatology of the length of the freeze-free season (bottom). Source: Mearns et al. (2009).
Figure 6.6: Water year precipitation (in inches) averaged over California (top), Great Basin (middle) and Colorado (bottom). Source: Bias Corrected and Downscaled World Climate Research Programme's CMIP3 Climate Projections archive at http:// gdo-dcp.ucllnl.org/downscaled_cmip3_ projections/#Projections:%20Complete%20 Archives.
Figure 6.7: Annual precipitation change (in inches) from the historical simulation for the low-emissions scenario (left), the high-emissions scenario (middle), and percentage of historical simulation compared to the high-emissions scenario (right). Early- (2021–2050), mid- (2041–2070) and late- (2070–2099) twenty-first century periods shown in top, middle and bottom panels. Values shown are the median of sixteen simulations downscaled via BCSD. Source: Bias Corrected and Downscaled World Climate Research Programme's CMIP3 Climate Projections archive at http://gdo-dcp.ucllnl.org/downscaled_cmip3_projections/#Projections:%20Complete%20Archives.
Figure 6.8: ARCCAP precipitation and temperature difference, June–September, 2041– 2069 relative to simulated historical means 1971-1999. The degree of change is indicated by the color, whereas the degree of agreement among the nine RCMs is indicated by the intensity of the color. For precipitation (left), the color intensity shows the agreement among the RCMs on the direction of change (i.e., positive or negative percent change in future precipitation); for temperature (right), the color intensity shows agreement among the RCMs on areas where future temperature is projected to be at least 2°C (3.6°F) higher than the 1971-1999 average. Source: Mearns et al. (2009).
Figure 6.9: Predicted changes in the water cycle. Mid-century (2041–2070) percent changes from the simulated historical median values from 1971-2000 for April 1 snow water equivalent (SWE, top), April–July runoff (middle) and June 1 soil moisture content (bottom), as obtained from median of sixteen VIC simulations under the high-emissions (A2) scenario. Source: Bias Corrected and Downscaled World Climate Research Programme's CMIP3 Climate Projections archive at http://gdo-dcp.ucllnl. org/downscaled_cmip3_projections/#Projections:%20 Complete%20Archives.
Figure 6.10: Spatially averaged values (in inches) for April 1 snow water equivalent (top), April–July runoff (middle) and June 1 soil moisture content (bottom). Averages are shown for California (left), Colorado (middle) and Rio Grande (right). Source: Bias Corrected and Downscaled World Climate Research Programme's CMIP3 Climate Projections archive at http://gdo-dcp.ucllnl.org/ downscaled_cmip3_projections/#Projections:%20Complete%20Archives.
Figure 6.11: High-emissions scenario mid-century (2041–2070) percent change from the historical period (1971–2000) for annual runoff. Data obtained from median of sixteen VIC simulations. Source: Bias Corrected and Downscaled World Climate Research Programme's CMIP3 Climate Projections archive at http:// gdo-dcp.ucllnl.org/downscaled_cmip3_ projections/#Projections:%20Complete%20 Archives.