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Number of 95 F days will quadruple in parts of Calif. -- study

Anne C. Mulkern, E&E reporter
Published: Friday, June 22, 2012

Climate change will heat up Southern California significantly by midcentury with higher temperatures overall and the number of extremely hot days tripling or quadrupling in many areas, a new study found.

The greater Los Angeles region will see temperature increases of 3.7 to 5.4 degrees Fahrenheit on average between 2041 and 2060, the report from the University of California, Los Angeles, predicts. All areas will see warming, but the valleys, inland areas, mountains and deserts will feel the worst impact.

The number of days when the thermostat hits 95 degrees or higher could increase to 34 annually from the current 10 in Riverside County, east of Los Angeles, the study says. And in the Palm Springs desert, those sweltering days could occur 119 times each year, compared with the current 75.

"The changes our region will face are significant, and we will have to adapt," said Alex Hall, study author and a professor in UCLA's atmospheric sciences department. "Every season of the year in every part of [Los Angeles] County will be warmer. This study lays a foundation for the region to confront climate change. Now that we have real numbers, we can talk about adaptation."

The changes will affect some 20 million people who live in Los Angeles and Orange counties, parts of Ventura, San Bernardino and Riverside counties, and sections of Palm Springs, Bakersfield and Santa Barbara. It is a region already struggling with access to water, and one needing growing amounts of electricity, problems that are expected to increase as temperatures climb, those involved with the study said.

The UCLA study is the latest to find that Southern California faces difficult warming over the next nine decades. David Pierce, climate researcher at Scripps Institution of Oceanography in San Diego, last month predicted that future heat waves will feature temperatures of at least 100 degrees Fahrenheit lasting three or more days. Temperatures as high as 110 degrees are probable, he found, if the world stays on its current path of high greenhouse gas emissions (ClimateWire, May 7).

The latest analysis from UCLA is the first in a planned five-part series, as the region looks for information to help with planning. Future studies will examine climate change's effects on precipitation, Santa Ana winds, soil moisture and coastal fog.

Los Angeles has created a framework for adaptation planning known as AdaptLA, which is looking at risk to public health, quality of life and public and private property.

"UCLA's model projects climate changes down to the neighborhood level, allowing us to apply the rigor of science to long-term planning for our city and our region," said Los Angeles Mayor Antonio Villaraigosa. "With good data driving good policies, we can craft innovative solutions that will preserve our environment and quality of life for the next generation of Angelenos."

'Deadly temperatures'

Hall said that he undertook the study because global climate models fail to take into account the affect of local topography. The greater Los Angeles region has a number of microclimates, with areas near the ocean much cooler on average than those that are on the other side of the Santa Monica Mountains or the famed Hollywood Hills.

The study showed that all regions will be affected by climate change but that there will be distinct differences. Areas along the coast will see a temperature increase of 3.5 to 4 degrees, while dense urban parts of Los Angeles will see a 4- to 4.5-degree climb and the deserts and mountains will warm 4.5 to 5.5 degrees.

But that does not mean the residents of beach cities will have it easy, Hall noted. Most of the homes in those areas lack air conditioning, meaning people there will have a more difficult time adapting to hotter weather. And the coast also will be wrestling with sea-level rise, he said.

"This is but one dimension of the changing climate," Hall said.

The extended days of high temperatures expected in the study have the potential to be deadly, looking at recent California and European heat waves as an example, said Paul Bunje, director of the Los Angeles Regional Collaborative for Climate Action and Sustainability (LARC), which along with the city of Los Angeles funded the UCLA study.

Past heat waves in the Golden State have killed. One in July of 2006 -- which was part of a North American hot streak that struck many states and Canada -- is blamed for 164 fatalities in California.

"Longer, harsher heat waves will cause more cases of heat stroke and heat exhaustion -- even among otherwise healthy people who believe they're immune," said Richard Jackson of UCLA's Fielding School of Public Health. "Higher temperatures mean more smog, with consequences for respiratory health, as well."

Heat waves also could affect transportation, as trains normally must slow down on extremely hot days, he said. That could affect the rest of the country, as 43 percent of all U.S. imports come through the ports of Los Angeles and Orange County and then are shipped eastward on trains, Bunje said.

And there is the issue of brush fires, which are exacerbated by hot, dry temperatures and the region's Santa Ana winds, Hall noted.

2 greenhouse gas scenarios

The UCLA study looked at two possible futures with climate change, one where the world stays on its current path with few efforts to shrink greenhouse gas emissions and another where there are mitigation measures adopted.

Under both scenarios, Hall said, Southern California will experience the uptick in temperatures and the increased days of hot weather by midcentury.

In the business-as-usual scenario, by the mid-21st century, the region will see an average temperature increase of 4.6 degrees Fahrenheit, the study says.

If there is mitigation, "the most likely warming and increase in heat extremes are somewhat smaller," the study said. "However, the majority of the warming seen in the business-as-usual scenario still occurs at all locations ... and heat extremes still increase significantly. Because it is very unlikely that humans will emit less greenhouse gases than in the mitigation scenario, adaptation to a changing climate over the next few decades is probably inevitable in the Los Angeles region."

Hall noted, however, that the finding does not mean the world should not make changes. If there is mitigation, he said, temperature increases plateau after midcentury and are not as extreme by 2100 as they would be under the business-as-usual approach.


Reprinted from ClimateWire with permission from Environment & Energy Publishing, LLC. www.eenews.net. 202-628-6500

 

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Reprinted from ClimateWire with permission from Environment & Energy Publishing, LLC. www.eenews.net. 202-628-6500.


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