USA: This is a worst-possible wildfire scenario for Southern California
By Eliza Barclay
This is part two in a three-part series about worst-case extreme weather scenarios in three regions of the United States — Arizona, California, and Florida — that are particularly vulnerable to the effects of climate change. In this story, we’ll consider a Big One that could ravage Southern California: a truly gargantuan wildfire that’s within the realm of possibility.
The wildfire that smashes all of California’s previous notions of “the worst that could happen” begins with an illegal firecracker set off by campers in the the San Bernardino National Forest. Patches of this forest, near the spa city of Palm Springs, have burned many times before. But this fire becomes monstrously big in a matter of hours because a severe, multi-year drought and an extra-long hot summer have left an unprecedented number of trees and shrubs bone dry, defenseless to flame.
This nightmare fire is hypothetical, created by a wildfire simulator, a computer model called FSim. Scientists use FSim to figure out extreme scenarios the environment is capable of, using data on historical weather patterns, available fuel on public and private lands, and several other variables.
It doesn’t predict specific wildfire events — that would be impossible, since every wildfire begins with an unpredictable ignition, or spark — but it imagines new fire seasons by recombining what has happened in the past. And every scenario it spits out is within the physical bounds of the possible.
Alan Ager, a researcher at the US Forest Service who studies how to manage wildfire risk on federally managed forests and other lands, found the 1.5 million-acre fire simulation in a database of simulated fires at the Missoula Fire Lab after I asked about the largest possible fire that could hit Southern California. I chose the region because it’s the most densely populated part of the state with very high wildfire hazard, according to the California Department of Forestry and Fire Protection, or Cal Fire.
“Climate change has created a new reality in the State of California. It’s not a question of ‘if’ wildfire will strike, but ‘when,’” said [Governor Gavin] Newsom in a June report. “Our recent, terrifying history bears that out. Fifteen of the 20 most destructive wildfires in the state’s history have occurred since 2000 and 10 of the most destructive fires have occurred since 2015. Wildfires don’t discriminate — they are a rural, suburban and urban danger. We all have an individual responsibility to step up and step in for our communities as we confront new and growing threats.”