Worsening Climate "Whiplash" Helps Explain Why California's Wildfires Were so Ferocious

At long last, the Eaton and Palisades wildfires in Los Angeles are almost fully contained.

It has been more than three weeks since the blazes erupted on Jan. 7, 2025, and now, as I'm writing this on Friday, Jan. 31, they are finally just a percent or two from full containment, according to the California Department of Forestry and Fire Protection.

Driven by hurricane force winds, the fires quickly roared through a desiccated landscape. Together they've scorched 37,469 acres — an area more than two and a half times the size of Manhattan.

As we've seen so tragically, entire neighborhoods have been reduced to ash and rubble, and at least 29 people have died. The fires now rank as two of the most deadly and destructive wildfires in California history.

Scientists are working hard to analyze the roles climate change may have played in the cataclysm. But to Daniel Swain, a climate scientist at U.C.L.A. and author of the Weather West blog, one factor seemed quite clear early on: a phenomenon known as "hydroclimate whiplash": a very wet period stimulating prolific growth of grass and brush, followed by a prolonged and intense dry spell that desiccates the vegetation, leaving the landscape with an overflowing tank of wildfire fuel.

Swain and other weather experts actually saw the Southern California cataclysm coming. He warned three days before of a "major, prolonged, and possibly extreme offshore wind and fire weather event." The wildfire risk would be very high, thanks to a bone-dry, fuel-rich Southern California landscape, along with warm temperatures and high winds that were forecast for Jan. 7.

"In terms meteorology, this was all too expected," Swain says. "The event and the risks were pinpointed with almost remarkable precision." And a good thing, too, because the forecast enabled pre-positioning of firefighting resources. The devastation and loss of life, as bad as they were, "arguably would have been much worse had we not had those predictions."

Swain also saw it coming from a longer-term perspective. The same week that he wrote his blog post, the journal Nature Reviews Earth & Environment published an article he co-authored titled, "Hydroclimate volatility on a warming Earth." The analysis revealed that human-caused warming is causing more frequent "whiplash" between very wet and very dry periods.

Swain and his co-authors found that globally, over the course of three-month "subseasonal" periods, the whiplash phenomenon has increased between 31 and 66 percent since the mid-twentieth century. Interannual whiplash, occurring on a 12-month timescale, had risen between 8 and 31 percent. And they warned that with further warming of 3 degrees C, whiplash would increase even more — by 113 percent sub-seasonally and 52 percent annually.

From this work, along with California's experience over the past few years, "it was clear that the southern part of the state faced an unusually high risk," Swain says. "Last winter was very wet, prompting extra growth of grass and brush." This was followed by "a record-breaking dry start to this year's rainy season, compounded by record-breaking heat at times."

In fact, Southern California experienced unusually generous precipitation not just last winter, but between 2022 and early 2024.

"The 2022-2023 water year, which runs from October through September, saw unrelenting atmospheric rivers that delivered torrential rain to California," according to NASA's Earth Observatory. "Much of the 2023-2024 water year was also wet, and rainfall totals for both periods, measured in downtown LA, were nearly twice the long-term average (1877-2024)."

The map above shows a satellite-based index of plant greenness during the summer prior to the fires. It reveals what copious precipitation produced. Many parts of Los Angeles County were 30 percent greener than average in summer of 2024.

By that time, the National Interagency Fire Center was already warning of copious growth of grasses and brush throughout California — with twice the normal amount in some hilly areas.

And then, dramatic whiplash. The Los Angeles region received no significant rain between May 2024 and early January 2025. The result is revealed by this image:

It shows moisture relative to normal in the top 40 inches of soil — the root zone — on January 7, 2025, the day the Palisades and Eaton fires ignited. All those areas of orange and red reveal dramatic desiccation.

In fact, soil moisture in much of Southern California was in the bottom 2 percent of historical records (1981-2013) for that day. That's historically low soil moisture, according to NASA.

It's important to keep in mind that there is no one reason why wildfire disasters are getting worse in some regions. "There's a confluence of factors," Swain says. "Climate change is one of them, but it's not the only one."

Among the others is our predilection for building in fire-prone areas. "There are just a lot more structures to hit now," he says. "Losses are going up because there are more people, more stuff, and more expensive assets in harm's way."

That said, "we do know that climate change is worsening wildfire risks in the areas most prone to it globally."

So, it's probably not a matter of if a disaster more horrific than L.A.'s will occur. It really is only a matter of when.