Climate Change Significantly Increased Likelihood of Extreme Fire Conditions in Los Angeles, Scientists Say
An international team of scientists reported Tuesday that climate change heightened the likelihood of the extreme conditions that fueled recent wildfires across the Los Angeles area.
According to a new study from the World Weather Attribution group, human-caused global warming made the hot, dry, and windy conditions leading up to the fires about 35% more likely.
The fires erupted during a powerful windstorm following an unusually dry stretch, with almost no rain in greater Los Angeles since spring. They have claimed at least 29 lives and destroyed over 16,000 structures, including homes, businesses, and schools.
“This was a perfect storm for fire disasters,” said John Abatzoglou, a climatology professor at UC Merced and a contributor to the report. “The climate set the stage, the weather drove the fires, and the densely built environment was directly in their path.”
The report highlights how human-driven warming has extended the region’s dry season, now averaging 23 more dry days per year compared to preindustrial times. This shift increases the likelihood of fires aligning with seasonal Santa Ana winds.
UCLA geography professor Park Williams, a co-author of the report, explained that Southern California’s cool-season fires require four key conditions: abundant dry vegetation, prolonged drought, an ignition source (almost always human-caused), and extreme weather, such as high winds. He likened each factor to a switch in a system that must be fully activated for a fire to ignite and spread.
“The artificial warming from human-caused climate change is making the light shine brighter,” Williams said.
To assess climate change’s role, researchers analyzed historical weather patterns and climate models, tracking shifts in the Fire Weather Index, a measure of temperature, humidity, and wind speeds—all critical factors in wildfire risk.
The study found that today’s climate conditions, which contributed to the recent L.A. fires, now occur roughly once every 17 years. Without climate change, such extreme conditions would have been expected only once every 23 years—and would have been less severe when they did happen.
World Weather Attribution, a collaborative group of scientists, conducts rapid analyses to assess the role of climate change in extreme weather events. While their findings undergo peer review, these quick-turnaround reports have not yet gone through the extensive academic review process that typically takes months or more. However, previous analyses on heatwaves, wildfires, and hurricanes have withstood scrutiny and were later published in academic journals.
Studying the exact impact of climate change on specific wildfire events is particularly challenging for climate attribution scientists, given the complex and localized nature of these disasters. In the case of the recent California fires, the report's authors concluded that while climate change was a contributing factor, it was not the sole cause of the catastrophic fires.
The hillsides around Los Angeles are covered in brush that naturally burns at regular intervals, and with increased human presence in these areas, the risk of fire ignitions—whether from cigarettes, power lines, fireworks, or vehicles—has risen. Moreover, neighborhood expansion into fire-prone zones has made homes both vulnerable to wildfires and contributors to their rapid spread.
“Fire in Southern California is highly complex,” said John Abatzoglou. “It’s a combination of many factors. This landscape has a significant human imprint.” He noted that the Los Angeles area faces challenges from its large population, frequent fire ignitions, and land-use issues.
The role of climate change in altering the Santa Ana winds, which play a crucial role in the spread of fires in Los Angeles, remains uncertain. Some studies suggest that these winds may weaken as the climate warms, while other research points to the possibility of the winds intensifying, particularly during colder months.
“We don’t know of a direct mechanism linking climate change to the winds, but there could be,” Park Williams said. “We just don’t know.”
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