Did Climate Change Worsen the Southern California Fires?
Given the scale of the blazes, and their increasing regularity, it makes sense to ask: Does global warming have anything to do with this?
The answer isn't as clear-cut as it was this summer, when drought- and heat-stoked fires raged across the Rockies and Pacific Northwest. Instead, a mix of forces are driving the fires in Southern California, and only some of them have a clear connection to global warming.
"These fires are not immediately emblematic of climate change," said John Abatzoglou, an associate professor of geography and climate at the University of Idaho, in an email. "Yes, California did have the warmest summer on record. But the big anomaly here is the delay in the onset of precipitation for the southland that has kept the vegetation dry and fire-prone." In other words, late-fall and winter rains would normally end California's fire season in November. Because those rains haven't yet arrived, the blazes continue. "At least in Southern California right now, we are largely seeing textbook wildfires," said Alexandra Syphard, a senior research scientist at the Conservation Biology Institute who studies fires. "Wind-driven fire events occur most typically in the fall, but can also occur like this, later in the year with fast-spreading, emberdriven
fires under Santa Ana wind conditions."
Santa Ana Winds
...But there are few signs -- at least so far -- that the Santa Ana winds are becoming more prevalent or that they're systematically moving later in the year. The peak of Santa Ana season usually comes in September or October. There is no trend toward more or fewer Santa Ana fires -- or Santa Ana winds generally -- in the historical record, Abatzoglou told me.
...There's currently a weak La Niña in the tropical Pacific, which means that global temperatures are cooler than they would be otherwise.
The same phenomenon is also keeping storms from making landfall in Southern California. Normally, California's wet season would have started by this time of year. "Once [autumn] rains hit the region, fuel moistures recover and make the landscape fire-resistant, thus reducing the odds that a power-line failure or vehicle will start a fire," said Abatzoglou. But the rains haven't yet appeared, he told me.