BERKELEY, California, August 5, 2008 (ENS) - In the near future, large California cities can expect more frequent heat waves because of climate change, warn scientists at universities in California and Texas.
This could mean increased electricity demand to run air conditioners in the densely populated state, raising the risk of power shortages during heat waves, said Norman Miller, an earth scientist at Lawrence Berkeley National Laboratory and geography professor at the University of California, Berkeley, and Katharine Hayhoe, a climate researcher at Texas Tech University.
If the electricity to run those air conditioners is generated using fossil fuels, this also could mean even more emissions of the heat-trapping gas carbon dioxide that causes climate change.
"Electricity demand for industrial and home cooling increases near linearly with temperature," said lead author Miller, a climate scientist and a principal investigator with the Energy Biosciences Institute in Berkeley.
"In the future," he said, "widespread climate warming across the western U.S. could further strain the electricity grid, making brownouts or even rolling blackouts more frequent."
When projected future changes in extreme heat and observed relationships between high temperature and electricity demand for California were mapped onto current availability of electricity, the researchers discovered a potential for electricity deficits as high as 17 percent during peak electricity demand periods.
Climate projections from three atmosphere-ocean circulation models were used to assess projected increases in temperature extremes and day-to-day variability, said Hayhoe.
Before the end of the century, projected increases range from about twice the current number of extreme heat days for inland California cities such as Sacramento and Fresno up to four times the number of extreme heat days for previously temperate coastal cities such as Los Angeles and San Diego.
This year, California experienced an unusually early heat wave in May, when 119 new daily high temperature records were set, including the earliest day in the year in which Death Valley temperatures reached 120 degrees. That occurred on May 19, beating the old record of May 25 set in 1913.
A second major heat wave in late July broke high temperature records for several more California cities and increased fire and health risks.
In the future, the authors say, the state should be prepared for summers dominated by heat wave conditions.
Similar increases in extreme heat days are likely for other urban centers across the Southwest, including Arizona, New Mexico, and Texas, as well as for large cities in developing nations with rapidly increasing electricity demands, the authors said.
Risk of electricity shortages can be reduced through energy conservation, said Hayhoe, as well as by reducing emissions of heat-trapping gases in order to limit the amount of future climate change that can be expected.
Miller and Hayhoe contributed to the Nobel Prize winning assessments of the UN's Intergovernmental Panel on Climate Change.
Miller is currently leading the BP-funded Energy Biosciences Institute project on biofuel productivity potentials, including biofuels' impact under changing climate conditions.
The Institute is a collaboration between the University of California-Berkeley, the University of Illinois at Urbana-Champaign, and Lawrence Berkeley National Lab working towards the development and analysis of the impacts of biofuels.
Their study was published in the "Journal of Applied Meteorology and Climatology" online.
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