As wildfires rage across Southern California, burning more than 1,000 homes, displacing nearly 100,000 people and paving a devastating trail of destruction, a San Diego researcher says climate change is playing a major role.
“The most unusual thing about this fire season is not the Santa Ana winds, it’s how dry it has been,” said Alexander Gershunov, a research meteorologist with Scripps Institution of Oceanography at UCSD.
Santa Ana winds typically peak in December and continue through February. The wind events are created by high pressure over the Four Corners region and lower pressure off the coast of California. The pressure gradient causes extreme dry winds to blow from the desert, up over the mountains and all the way to the coast.
"What we clearly see is although there’s not much of a change in Santa Ana wind activity over the last 70 years or so, what we see is that we’re losing precipitation," Gershunov said.
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The wind events this season have exacerbated San Diego County’s historic dry spell, he said.
“We’ve had two-tenths of an inch of precipitation and we’re in mid-December,” Gershunov said. “And there’s no rainfall in the forecast.”
According to the National Weather Service, the region should have received nearly 2 inches of rainfall by now, moistening the vegetation and dampening the risk of fire.
But the last time San Diego received significant rainfall was in March, when the region’s canyons and hills were covered in wildflower super blooms. Nine months later, vegetation is bone dry, putting the entire county at a high risk for fire.
Gershunov, who studies long-term records of weather events and weather extremes, said extended dry periods will become a new normal as the climate warms.
“What we see is that we’re losing precipitation — basically storms in the autumn and the spring,” Gershunov said. “That’s a trend that’s clearly linked to climate change.”
“What happens with climate change is that the subtropical zone is expanding towards polls, and that basically pushes storms out,” he explained.
The longer timeframe of no rainfall means a longer period for vegetation to dry out, and an increased threat of wildfires.
A three month weather outlook by NOAA’s Climate Prediction Center shows continued overall warm and dry conditions in San Diego County.
Gershunov said the region will be under the threat of wildfires until it rains, and beyond.
“Unfortunately, this season is an example of what we expect to see more and more of in the future,” he said.
