Two large wildfires that exploded on January 7 in Los Angeles were the most destructive and potentially the costliest in the city's history.
Still burning after three weeks, the Palisades and Eaton fires have so far caused 28 known fatalities and the destruction of more than 16,000 structures.
The warm, arid and well-forested West Coast of the US has a long history of catastrophic wildfires. But a new study has found that climate change caused by burning fossil fuels has made the problem a lot worse.
The hot, dry and windy conditions that drove the LA fires were about 35% more likely due to climate change, according to World Weather Attribution (WWA), a collaboration of global scientists analyzing climate change's influence on extreme weather events.
Global temperatures have increased 1.3 degrees Celsius since pre-industrial times, while 2024 was the hottest year on record.
The added heat made the unusually low rainfall from October-December more likely, and also significantly increased the intensity of the dry, Santa Ana winds that whipped up the flames, said the study's authors.
"All across the western and southern US we expect to see increasing drying effects with climate change, meaning more flammable conditions," noted Theo Keeping, a lead author of the WWA study, who researches global wildfires at the University of Reading in the UK.
"The likelihood of these events is growing much faster than during previous decades," he added.
The fact that the blazes occurred in winter is not unprecedented. However wildfires are typically larger in the summer from July to September.
Human-induced climate change has altered the likelihood and intensity of the fire-prone weather fueling the LA wildfires to the extent that such conditions now occur every 17 years, as opposed to every 23 years in the pre-industrial climate, noted Keeping. However, this figure discounts scientific uncertainties related to high climatic variability in the region.
If the world continues to heat at current rates and temperatures increase by 2.6 degrees by the end of this century, the likelihood of extreme wildfires increases by another 35%, the scientists found.
Climate 'whiplash' increases wildfire intensity
A heating planet is behind a weather phenomenon known as "hydroclimate whiplash," which sees one year of intense rainfall followed by one year of drought.
Warmer air causes the atmosphere to hold more moisture. But while "it can dump that moisture," a hotter atmosphere can also "suck that moisture up much more easily," Keeping explained.
The higher precipitation increases lush vegetation, resulting in a greater frequency of high fuel load — which occurred in 2023, according to the lead author.
But in 2024 expected October-December rainfall never arrived, drying out the grown forest, or flame-fuel, and increasing the intensity of the wildfires.
This climate whiplash will continue to cause "more devastating wildfire events" in the future, said Keeping.
Overall, the length of the dry season in Southern California has increased by 23 days compared to when the global climate was 1.3 degrees Celsius cooler, according to climate models employed in the WWA study.
With the LA region not having received regular rainfall since May 2024, the fire-prone conditions were further fueled by dry Santa Ana winds that happen from October-March when it is typically cooler.
The overlapping impact of these dry winds on a fire-prone cool season is often underrepresented in climate models, the scientists wrote in the study.
"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,” explained Clair Barnes, World Weather Attribution Researcher at the Centre for Environmental Policy, Imperial College London.
Study confirms global wildfire trend
The WWA report is one of numerous recent studies that attribute devastating wildfire extremes to human-induced climate change — including in Canada in 2023 and Brazil in 2024.
The LA study notes that the latest assessment by the Intergovernmental Panel on Climate Change (IPCC) indicates that rising temperatures are creating fire-prone weather conditions globally, including in Mexico and across western and northwestern North America.
"When we look across all of the scientific literature there's a very clear increasing wildfire risk in lots of parts of the world," said Keeping.
The WWA researchers reiterate that the climate change fueling the flames is "primarily driven by the burning of fossil fuels."
"Without a faster transition away from planet-heating fossil fuels, California will continue to get hotter, drier, and more flammable," Barnes said.
