Southern California Wildfires Show Split Personalities: Climate Change is Contributing to More intense Wildfires

LOS ANGELES, CA - 9/9/2015 (PRESS RELEASE JET) -- Wildfires have ravaged regions of Southern California at an increasing rate over the past few decades, and scientists from three University of California campuses and partner institutions are predicting that by mid-century, a lot more will go up in flames.

In research published Tuesday in the journal Environmental Research Letters, the scientists discuss the split-personality nature of Southern California wildfires. They describe two distinct wildfire regimes, those driven by offshore Santa Ana winds that kick up in the fall and non-Santa Ana fires that result primarily from hot, dry conditions in the summer.

 “The traditional one-size-fits-all fuel management strategy will not be effective in reducing fire risks and preventing large fires,” said lead author Yufang Jin, assistant professor in the Department of Land, Air and Water Resources at UC Davis and a researcher at UC Irvine at the time of the study. “California and the western U.S. are expected to face increased fire risk as the current multi-year drought continues. Local meteorology, extreme climate events, and ecosystem processes must be explicitly considered to develop effective mitigation and adaptation strategies.”

The essential climate findings were these:

• 64%: the area burned by Santa Ana fires increases by 64%, mainly because four of the five global climate model projections showed more intense Santa Ana wind events.
• 77%: the area burned by non–Santa Ana fires increases by 77%, mainly because of an increase in temperatures.
• 20% and 74%: the number of structures destroyed by Santa Ana fires increases by 20%, and the number of structures destroyed by non–Santa Ana fires increases by 74%.

The two fire regimes consume roughly the same amount of acreage and cost similar amounts to suppress. However, the Santa Ana fires, which tend to hit more developed areas, such as the coastal areas of Los Angeles and San Diego, are roughly 10 times more economically damaging.

Compared to non-Santa Ana fires, Santa Ana fires:

• Spread three times faster
• Burned into urban areas with greater housing values
• Were responsible for 80 percent of the $3.1 billion in economic losses occurring over the study period of 1990 to 2009.

“Warming in the summertime will be a big factor in increasing the size and duration of non-Santa Ana fires,” said co-author Alex Hall, UCLA professor of atmospheric and oceanic studies. “Expected lower relative humidity resulting from climate change toward the middle of the century will lead to Santa Ana fires of greater intensity.”

Fire-prone regions also face increased competition during the summer for firefighting resources, such as air tankers, vehicles, and personnel. “The large economic and human impacts of Santa Ana fires raises the question of whether more resources during the fall could be marshaled for suppressing these fires,” said James Randerson, Chancellor’s Professor of Earth system science at UCI and senior author on the paper.

“Governor Brown’s executive order B-30-15, issued in April 2015, tasks the state to identify climate-related vulnerabilities” said Jonathan Parfrey, executive director of Climate Resolve. “This important study unveils an enormous threat facing Southern California. We need to take this study seriously and pursue action.”

The researchers relied on satellite data from NASA’s Jet Propulsion Laboratory and decades’ worth of fire records from the California Department of Forestry and Fire Protection (CAL FIRE) and the U.S. Forest Service. The study was funded by NASA and the Jenkins Family Foundation.

Climate Resolve, a Los Angeles-based nonprofit organization dedicated to creating real, practical solutions to meet the climate challenge in Los Angeles, works with climate scientists on highlighting climate studies that impact Southern California today and in the future.

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