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1 day ago
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A triple whammy of climate impacts boosted the risk of the ferocious fires that recently ravaged Los Angeles, a scientific study has shown.
Firstly, the hot, dry and windy conditions that drove the fires were made 35% more likely by the global heating caused by fossil fuel burning. Secondly, the low rainfall seen from October to December is now about 2.4 times more likely than in the preindustrial past, before the climate crisis. Rains during these months have historically brought an end to the wildfire season around LA.
Thirdly, conditions of high fire risk have extended by more than three weeks in today’s heated climate, now reaching into January. This means fires have more chance of breaking out during the peak Santa Ana winds, which can blow small fires into deadly infernos.
The extreme fires began blazing around LA on 7 January. Powerful mountain winds drove the fires through tinder-dry vegetation and into urban areas. At least 28 people were killed and more than 10,000 homes destroyed. The fires are the most destructive in LA’s history and may be the costliest in US history.
The study was carried out by 32 US and European experts working as part of the World Weather Attribution (WWA) collaboration. The demonstration of a clear link to the climate crisis runs counter to the flood of disinformation that followed the fires, which included falsely blaming fish protections, a mass plot related to high-speed rail, and diversity measures.
“Climate change increased the risk of the devastating LA wildfires,” said Dr Clair Barnes, at Imperial College London, UK, who led the study. “Without a faster transition away from planet-heating fossil fuels, California will continue to get hotter, drier and more flammable.”
The study used weather data and climate models to compare the likelihood of fire conditions in today’s hotter climate with the likelihood in an unheated preindustrial climate. Hundreds of peer-reviewed studies have used these methods before. The weather data and models clearly showed an increased risk of hot, dry and windy conditions due to human-caused global heating.
The weather data also showed the low rainfall and extended dry period were significantly more likely today. In these cases, the climate models showed considerable uncertainties, because only a small area was being studied and winds are highly variable in mountainous regions.
Nonetheless, the scientists said: “Given all the lines of evidence we have high confidence that human-induced climate change increased the likelihood of the devastating LA fires.” A preliminary study looking only at the hot, dry and windy conditions also found that climate change was a factor in the LA fires. Globally, scientists agree that climate change is increasing the global risk of wildfires starting and spreading as persistent heat dries out soils and vegetation.
Roop Singh, at the Red Cross Red Crescent Climate Centre, said: “A deadly combination of factors came together to turn this wildfire into a disaster – climate change set the stage. These fires have highlighted just how vulnerable California is to winter wildfires, underscoring the need for better preparation for a more dangerous future.”
The study highlighted issues with the water infrastructure that was unable to keep up with the extreme needs during the Eaton and Palisades wildfires. Officials have said power outages meant pumps were unable to operate. The WWA team also emphasised the importance of early warning and evacuation systems as 17 of the 28 deaths occurred in west Altadena, a neighbourhood with high African American home ownership, and where warnings were delayed compared with other affected areas.
Dr Friederike Otto, at Imperial College London and a co-lead of WWA, said: “From violent hurricanes in the east, to nightmarish wildfires in the west, Americans are experiencing the devastating consequences of fossil fuel warming. In 2025, the choices facing world leaders remain the same – to continue to burn oil, gas and coal and experience ever more dangerous weather, or transition to renewable energy for a safer and fairer world.”
New US president Donald Trump has pledged to “drill, baby, drill” and pulled the US from the Paris climate agreement, joining only a handful of war-torn states– Libya, Iran and Yemen. However, many other countries remain committed to climate action.
The LA fires were an example of climate “whiplash” between extremely wet and dry conditions which exacerbates disasters and which are increasing exponentially around the world because of global heating. In LA, wet conditions in the previous two years enabled strong growth of vegetation, providing fuel for the fires when dry conditions returned.
Toxic smoke from the LA fires has also affected millions of people and will claim further lives. A global study published in November found that from 2000 to 2019 about 1.5m deaths a year were associated with the dirty air caused by wildfires. Heart attacks, strokes and respiratory deaths are the most common, but worsened diabetes, kidney disease and mental health also contribute.
In North America, there have been more than 25,000 deaths a year on average from wildfire pollution, with the number rising by 3% a year over that time. “[The pollution] often travels hundreds and even thousands of kilometres away and affects much larger populations than flames and heat do,” said Prof Yuming Guo at Monash University, Australia, who led the study.
An editorial in the Lancet medical journal last week said: “The evidence is clear on the increasing risk of wildfires due to climate change, and the impact on physical and mental health. Will the California wildfires make [politicians] face reality? Turning away is bringing harms and destruction that are increasingly impossible to ignore.”
