From the first reports of wildfires breaking out around Los Angeles earlier this month, scientists could say that climate change had worsened the blazes. Sure, wildfires would burn in California regardless of planetary warming, but extra-dry fuels had turned the landscape into tinder. The resulting blazes, fanned by 100-mile-per-hour Santa Ana wind gusts, burned 50,000 acres. They killed at least 28 people and destroyed more than 16,000 structures, causing perhaps hundreds of billions of dollars of damage and economic losses.

A more thorough analysis published Tuesday found that those extremely dry and hot conditions were about 35 percent more likely thanks to climate change. Rains starting in October normally dampen the Southern California landscape, reducing wildfire risk, but the almost nonexistent rainfall this autumn and winter was about 2.4 times more likely when compared to a preindustrial climate, according to the study by World Weather Attribution, a U.K.-based research group. The region now has 23 additional days of fire-prone conditions each year, the analysis found, meaning more opportunities for blazes to spread out of control. 

“Drought conditions are more frequently pushing into winter, increasing the chance a fire will break out during strong Santa Ana winds that can turn small ignitions into deadly infernos,” said Clair Barnes, a World Weather Attribution researcher at Imperial College London’s Centre for Environmental Policy, in a statement. “Without a faster transition away from planet-heating fossil fuels, California will continue to get hotter, drier, and more flammable.”

A major driver of these catastrophic wildfires is “weather whiplash,” the report notes. Wet seasons are getting wetter, a result of a hotter atmosphere being able to hold more moisture, while dry seasons are getting drier. In the two previous winters, Los Angeles got significant rainfall, leading to the explosive growth of grasses and shrubs. But then an atmospheric switch flipped, and the metropolis got almost no rainfall between May 2024 and this January, so all that extra vegetation dried out. “Very wet years with lush vegetation growth are increasingly likely to be followed by drought, so dry fuel for wildfires can become more abundant as the climate warms,” said Theo Keeping, a wildfire researcher at Imperial College London’s Leverhulme Centre for Wildfires and co-author of the report, in the statement.

In a separate analysis released on January 13, researchers at the University of California, Los Angeles, found that climate change could be blamed for roughly a quarter of the dryness of the vegetation that burned in the fires, which they described as a conservative estimate. The study also found that the region’s weather whiplash set the stage for disaster. “Under a warmer climate, you also have what people would call a ‘thirstier’ atmosphere trying to draw up as much moisture as it can,” said Chad Thackeray, a climate scientist at UCLA and co-author of the report. 

And then came the seasonal Santa Ana winds at the start of January, which blew strong and dry. In a matter of hours or even minutes, that air can desiccate the vegetation further still. All it took was sparks for several wildfires to rapidly spread. The Santa Ana winds not only shoved those fires along with breathtaking speed, but also created unpredictable swirls that made the blazes behave erratically. That made the wildfires exceedingly difficult to fight — especially for crews already spread thin fighting on multiple fronts, as the disabled and elderly in particular struggled to evacuate in time. “Realistically, this was a perfect storm when it comes to conditions for fire disasters,” said John Abatzoglou, a climatologist at the University of California, Merced, and co-author of the World Weather Attribution report, on a press call Tuesday morning.

And conditions in Southern California will probably get worse from here. The World Weather Attribution analysis estimates that fire-prone conditions in the region will become 35 percent more likely still if the world warms by 2.6 degrees Celsius above preindustrial levels.

For as much as climate change influenced the Los Angeles wildfires, a few factors operate separately. For one, climate change doesn’t create Santa Ana winds. And scientists don’t expect Santa Ana winds to get stronger as the planet warms — they might even get slightly weaker — though that will require more research to fully tease out. And two, humans spark the vast majority of wildfires in California, be it with electrical lines, fireworks, or arson. And lastly, developers keep building homes in the densely vegetated “wildland urban interface,” where the risk of wildfire is extreme.

This growing risk presents a daunting challenge for communities as they rebuild. Homeowners, for instance, have to keep their yards clear of vegetation and adopt fire-proof building materials, which gets expensive. “Communities can’t build back the same because it will only be a matter of years before these burned areas are vegetated again and a high potential for fast-moving fire returns to these landscapes,” said Park Williams, a geographer at UCLA and co-author of the World Weather Attribution report, in the statement.