Summary for Decision Makers reviews the past, present, and projected future climate of the Southwest; discusses the effects of climate changes on ecosystems, the coastal zone, water resources, human health, and other areas; and presents the choices that society can make to adapt to climate change, based on what we know and within the constraints of what we don’t know.
Citation:
Overpeck, J., G. Garfin, A. Jardine, D. E. Busch, D. Cayan, M. Dettinger, E. Fleishman, A. Gershunov, G. MacDonald, K. T. Redmond, W. R. Travis, and B. Udall. 2013. “Summary for Decision Makers.” 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, 1–20. A report by the Southwest Climate Alliance. Washington, DC: Island Press.
Jonathan Overpeck (University of Arizona)
Gregg Garfin (University of Arizona)
Angela Jardine (University of Arizona)
David E. Busch (U.S. Geological Survey)
Dan Cayan (Scripps Institution of Oceanography)
Michael Dettinger (U.S. Geological Survey)
Erica Fleishman (University of California, Davis)
Alexander Gershunov (Scripps Institution of Oceanography)
Glen MacDonald (University of California, Los Angeles)
Kelly T. Redmond (Western Regional Climate Center and Desert Research Institute)
William R. Travis (University of Colorado)
Bradley Udall (University of Colorado)
Figure Gallery
Figure 1.1: Rapid population growth in the Southwest is expected to continue. The current (2010) population is 56 million, and an additional 19 million people are projected to be living in the region by 2030. Source: US Department of Commerce, Bureau of Economic Analysis http://www.bea.gov/regional/ index.htm. [Chapter 3]
Figure 1.2: Temperature trends in the twentieth century. The 1901–2010 trends in annually averaged daily maximum temperature (TMAX, top) and daily minimum temperature (TMIN, bottom). Units are the change in °C/110yrs. Trends computed from 251 stations for precipitation analysis and 180 stations for temperature analysis using GHCN V3 data. Source: Menne and Williams (2009). [Chapter 5]
Figure 1.3: History of drought in the West. Percent area affected by drought (PDSI)
Figure 1.4: Changing streamflow timing 2001–2010 compared to 1950–2000. Differences between 2001–2010 and 1950–2000 average date when half of the annual streamflow has been discharged (center of mass) for snowmeltdominated streams (Stewart, Cayan and Dettinger 2005). [Chapter 5]
Figure 1.5: 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). [Chapter 6]
Figure 1.6: 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). [Chapter 6]
Figure 1.7: 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 highemissions (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:%20Complete%20 Archives. [Chapter 6]
Figure 1.8: Areas of the western United States burned in large (> 1000 acres [400 ha]) fires, 1984–2011. Dark shading shows fires in areas classified as forest or woodland at 98-feet (30-meter) resolution by the LANDFIRE project (http://www.landfire.gov/). Fire data from 1984–2007 are from the Monitoring Trends in Burn Severity project (http://www.mtbs.gov/) and fire data from 2008–2011 are from the Geospatial Multi-Agency Coordination Group (http://www.geomac.gov/). [Chapter 8]
Figure 1.9: Past, present, and future sea-level rise. Geologic and recent sea-level histories (from tide gauges and satellite altimetry) are combined with projections to 2100 based on climate models and empirical data. Modified with permission from Russell and Griggs (2012), Figure 2.1. [Chapter 9]
Figure 1.10: Compounding impacts of drought on energy. [Chapter 12]
Figure 1.11: Extensive federal lands in the Southwest: A legacy for the future. This map illustrates the legacy of federal land ownership in the Southwest, covering nearly 30 percent of the entire United States. Protected habitat and ecosystem services ensure sustainable management of resources and may be the greatest insurance policy against losses in the future, because natural resource use and biological species can more easily adapt to rapidly changing climatic conditions. Modified from The National Atlas of the United States of America (http://www.nationalatlas.gov; see also http://nationalatlas.gov/printable/images/pdf/fedlands/fedlands3.pdf; accessed October 8, 2012). [Chapter 18]