Climate change did not ignite the recent blazes that engulfed swathes of Los Angeles this month. But it did make them worse in at least one key way, a rapid analysis has found.
The fires that erupted on 7 January astounded officials as they ballooned in size in mere hours, torching famous neighbourhoods, forcing 190,000 people to evacuate and taking 28 lives.
President Donald Trump has been engaged in a spat with state governor and political foe Gavin Newsom about who is to blame for the fires before the two had an apparently amicable meeting on Friday.
The early sparks were fanned into infernos by the now infamous Santa Ana winds – hot, dry winds most common in winter, which reached 99mph. Scientists do not yet understand if climate change disrupts these parching winds.
But global warming made the hot and dry conditions that drove the ferocious fires about 35% more likely and 6% more intense, a global network of 32 scientists at World Weather Attribution (WWA) said today.
The world is already on average 1.3C hotter than before humans started burning fossil fuels at scale.
Around Los Angeles, the hotter air dried out the shrubby vegetation in the area called chaparral, turning it into tinderbox material that feeds a fast-moving fire.
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They also found the fire season, with highly flammable drought conditions, in Los Angeles lasts 23 days longer per year, and that low rainfall between October and December is more than twice as likely.
While climate change influenced these two trends, they cannot yet quantify the extent, due to the complex local geography and a lack of data, they said.
Dr Clair Barnes from WWA and Imperial College London said: “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.
“Without a faster transition away from planet-heating fossil fuels, California will continue to get hotter, drier, and more flammable.”
John Abatzoglou, professor of climatology at the University of California Merced, who also worked on the study, said: “This was a perfect storm of climate-enabled and weather-driven fires impacting the built environment.”
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The ‘fundamental solution’ to preventing more fires
Last week, President Trump threatened to block federal disaster funding for Los Angeles unless governor Gavin Newsom enforced voter ID and made changes to the city’s water management.
Mr Trump, who last week ripped up scores of environmental rules, has repeated spurious claims that the conservation programme for a tiny fish caused the fire hydrants to run dry.
The scientists called for an overhaul of water infrastructure, which is designed for more routine, structural fires, but now needs to handle intense continuous needs of a fast-moving wildfire.
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They also pointed the finger at other policies that had nothing to do with climate change, including housing being built in fire-prone areas.
Governor Newsom has commissioned an independent investigation into the loss of water pressure to hydrants.
Patrick Gonzalez, a climate change scientist and forest ecologist at California’s Berkley University, who was not involved with the study, said: “Most importantly, the fundamental solution to prevent catastrophic wildfires is cutting the carbon pollution from cars, power plants, and other human sources that causes climate change.”
‘Take this seriously’
The researchers reached their findings by comparing a computer simulation of the conditions with a simulation of the climate had it not been warmed by humans, and drawing on existing research.
It follows previous studies from the University of California, Los Angeles (UCLA) that found climate change was to blame for about a quarter of the fuel available for the fires.
The quick analysis has not been formally peer-reviewed, as it would have to be to get published in a scientific journal, but uses peer-reviewed methods.
Dr Gonzalez said it is “consistent with published research showing that human-caused climate change has intensified the heat that drives wildfire”.
Prof Gabi Hegerl, a climate scientist from Edinburgh University who was not involved with the study, called it a “carefully researched result that should be taken seriously”.
