More, hotter heat waves predicted for Southern California
Southern California is going to feel the heat in the coming years, according to a new UCLA climate change study.
The study, released Thursday, is the first to model the Southland's complex geography of meandering coastlines, mountain ranges and dense urban centers in high enough resolution to predict temperatures down to the level of micro climate zones, each measuring 2¼ square miles. The projections are for 2041 to 2060.
The number of days with temperatures above 95 degrees each year will triple in downtown Los Angeles, quadruple in portions of the San Fernando Valley and even jump five-fold in a portion of the High Desert in L.A. County, according to the study.
Not only will the number of hot days increase, the study found, but the hottest of those days will break records, said Alex Hall, lead researcher on the study by UCLA's Institute of the Environment and Sustainability. The record high for downtown Los Angeles is 113 degrees, set Sept. 27, 2010, when the Department of Water and Power reported that electricity demand reached a historic peak of 6,177 megawatts.
Mayor Antonio Villaraigosa said the forecasts provide the groundwork for local governments, utilities, hospitals and other institutions to prepare for the hot spells to come. Villaraigosa said the region may have to strengthen building codes to reduce risk to residents. "That could mean replacing incentives with building codes requiring 'green' and 'cool' roofs, cool pavements, tree canopies and parks," he said.
The study, aided by a UCLA supercomputer, is 2,500 times more precise than previous climate models for the region, said Paul Bunje, executive director of the UCLA Center for Climate Change Solutions. The computer made roughly 1 quintillion calculations — the equivalent of eight times all the grains of sand on the beaches of the western United States — over a period of six months to assess every aspect of 25 global warming models that might be applicable to Southern California.
The computer found, for example, that the number of days per year the temperature exceeds 95 degrees is likely to increase from eight to 30 in Porter Ranch, from 55 to 91 in Bakersfield and from 75 to 119 in Palm Springs. In the L.A. County High Desert community of Palmdale, temperatures will rise above 95 degrees 33 days a year, up from seven currently, according to the analysis.
Los Angeles, fanned by ocean breezes, will see 95-and-over days increase a relatively modest threefold from the current 1½ per year. The Santa Monica Mountains are enough of a barrier to cooler ocean influences that the San Fernando Valley will warm 10% to 20% more than the L.A. Basin.
More generally, the research showed that oceans and coasts are likely to warm by 2 to 3 degrees, dense urban areas by 4 degrees, and mountains and deserts by 4 to 5 degrees.
-- Louis Sahagun
Photo: Bathers escape the heat at Santa Monica Beach. Credit: Lawrence K. Ho / Los Angeles Times