Projected California Warming Creates Cycle of More Heat Waves, Energy Use for 21st Century

As the 21^st century progresses, major cities in heavily air-conditioned California can expect more frequent extreme-heat events caused by climate change. This could mean increased demand for electricity in the densely-populated state which may increase the risk of power shortages during heat waves, said Katharine Hayhoe, a climate researcher in the Department of Geosciences at Texas Tech University who co-authored the report with researchers from the University of California, Berkeley. If additional electricity were generated through fossil fuels, this could mean even more emissions of heat-trapping gasses that cause climate change. "Risk of electricity shortages can be reduced through energy conservation as well as through reducing our emissions of heat-trapping gasses in order to limit the amount of future climate change that can be expected," Hayhoe said. The results were published in the online version of the Journal of Applied Meteorology and Climatology. Researchers used climate projections from three atmosphere-ocean general circulation models to assess projected increases in temperature extremes and day-to-day variability. Before the end of the century, increases in extreme heat days could range from approximately twice the present-day number for inland California cities such as Sacramento and Fresno, to up to four times the number for previously temperate coastal cities such as Los Angeles and San Diego. "Electricity demand from industrial and home space cooling already increases as a near linear response to outdoor temperatures," said Max Auffhammer, an assistant professor of agriculture and resource economics at the University of California, Berkeley. "With widespread increase in extreme heat days across the Western U.S., the electricity grid could be further strained and brownouts and rolling blackouts may become more frequent." This year, California experienced an unusually early heat wave in May that set 119 new daily high temperature records. On May 19, Death Valley set a record for the earliest day to reach 120 degrees, breaking the May 25, 1913, record. Now in its second heat wave this summer, record high temperatures have been broken for several more California cities in recent days. "In the future, the state should brace for summers dominated by the heat-wave conditions, such as those experienced this year," said Norman Miller, lead author of the study and a climate scientist at Lawrence Berkeley National Laboratory. "Extreme heat and heat-wave events have already triggered major electricity shortages like those seen in the summer of 2006. Given past events, the results of this study suggest that future increases in peak electricity demand may challenge the current and future electricity supply and transmission capacities." When the projected extreme heat and observed relationships between high temperature and electricity demand for California are mapped onto current availability, the researchers discovered a potential for electricity deficits as high as 17 percent during peak electricity demand periods. Similar increases in extreme-heat days are likely for other urban centers in Arizona, New Mexico and Texas, as well as for large cities in developing nations with rapidly increasing electricity demands. Hayhoe and Miller also contributed to the Nobel Prize-winning United Nations Intergovernmental Panel on Climate Change. For a PDF copy of the report, please contact John Davis at Texas Tech University. CONTACT: Katharine Hayhoe, associate professor, Department of Geosciences, Texas Tech University, (806) 392-1900, or katharine.hayhoe@ttu.edu. Norman Miller, climate scientist, Earth Sciences Division, Lawrence Berkeley National Laboratory, (510) 495-2374 or NLMiller@lbl.gov.