Camp Fire, the devastating blaze raging across the Sierra Nevada foothills, has become the most destructive wildfire in California’s history. By the evening of Nov. 10, it had scorched 105,000 acres of land and killed 23 people, with more than 100 people still unaccounted for.
“This event was the worst-case scenario,” Butte County Sheriff Kory L. Honea told the Washington Post (paywall). “It’s the event that we have feared for a long time.”
In all likelihood, it’s a scenario that climate change helped to create, according to Daniel Swain, a researcher at University of California-Los Angeles’ Center for Climate Science. In a detailed thread on Twitter, Swain walked through the conditions that contributed to the fires now burning across the state, and the research showing how climate change made them possible.
His analysis offers sobering view of the role global warming can play in such disasters—”a calm and comprehensive scientific account of why climate change makes fires like the ones now shrouding California more likely and more hellish,” according to renowned environmental activist Bill McKibben.
While climate change didn’t itself cause the fire, Swain explains, it played a “starring role.” Summers in the state have been getting hotter, and autumns have been getting both warmer and drier. “While the exact level of dryness in a particular year is somewhat random, less precipitation in autumn & spring—California’s ‘shoulder seasons’—has long been a projected outcome of climate change,” he adds.
The result is a practical tinder box of dry vegetation at a time when California tends to experience strong offshore winds—a ready-made recipe for fast-spreading wildfires. Urban development in areas that are already at risk for wildfires has only compounded the problem.
Swain and his colleagues warned about the growing threat of massive fires in an August story for The Guardian. Climate change, they wrote, has acted as a “threat multiplier.”
Notable, too, is that climate change doesn’t seem to be increasing the frequency of wildfires so much as their character. It’s making them more intense, and likely to spread faster. “In California,” the researchers noted, “not all wildfires are forest fires—some of the state’s deadliest and fastest-moving fires have burned primarily in shrubs and oak woodlands. With climate change tipping the scales in favor of hotter temperatures and drier conditions across the entire landscape, vegetation of all types is becoming more flammable.”
To that point: The deadly fires burning in California right now are not actually forest fires, despite Donald Trump’s tweet that forest management was to blame. They were fueled, the Los Angeles Times reports, by “dry grass growing amid scattered pine and oak trees.”