‘A perfect storm’: How climate change made the LA wildfires more likely - and more deadly

Human-caused climate change worsened the devastating Los Angeles wildfires, a new study has found.

Fossil fuel burning reduced rainfall, dried out vegetation, and increased the overlap between flammable drought conditions and strong Santa Ana winds, aggravating the blazes.

The study was carried out by 32 researchers, including leading wildfire scientists from the US and Europe.

They form part of World Weather Attribution, an academic group that has studied the influence of climate change on more than 90 extreme events around the world.

The scientists also warn that LA will get drier and more flammable with continued fossil fuel burning.

Climate change made LA wildfires 35% more likely

Extreme fires broke out around Los Angeles, California, on 7 January. Fanned by powerful Santa Ana mountain winds and burning through tinder-dry vegetation, the fires rapidly spread into urban areas.

They eventually killed at least 28 people, more than 10,000 homes have been destroyed, and millions are still being affected by toxic smoke. The fires are the most destructive in LA’s history and potentially the costliest in US history.

The study found that the hot, dry and windy conditions that fuelled the LA fires were about 35 per cent (1.35 times) more likely due to climate change.

These fire-prone conditions will intensify if countries keep burning fossil fuels, the researchers warn.

At 2.6°C of warming, which is expected by 2100 under current scenarios, similar fire-weather in January will become a further 35 per cent more likely, making similar extremes about 80 per cent (1.8 times) more likely compared to the 1.3°C cooler preindustrial climate.

“Without a faster transition away from planet-heating fossil fuels, California will continue to get hotter, drier, and more flammable,” said Dr Clair Barnes, World Weather Attribution researcher at the Centre for Environmental Policy at Imperial College London.

Climate change has extended fire-prone conditions in LA by 23 extra days a year

The researchers also found the LA wildfire season is becoming longer and more dangerous as fossil fuel emissions heat the climate.

Highly flammable drought conditions now last about 23 more days each year on average than in the preindustrial climate, an analysis of historical weather data found.

Due to highly variable rainfall, drought conditions can last much longer in some years, the scientists say.

October to December rainfall has historically brought an end to the wildfire season. But in recent decades, these rains have decreased.

Today, low rainfall across the three months is about 2.4 times more likely in neutral El Niño conditions, and a further 1.8 times more likely in La Niña conditions compared to the preindustrial climate.

The two weather phenomena influence the temperatures of the Pacific Ocean which can affect weather patterns around the globe.

Hotter air temperatures are also evaporating more moisture from plants, making them easier to burn.

“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 Barnes.

LA wildfires: Climate change created a ‘perfect storm’

The researchers note that while the individual results of these analyses show some degree of uncertainty, they point in the same direction, indicating that climate change increased the likelihood of the fires.

“This was a perfect storm of climate-enabled and weather-driven fires impacting the built environment,” said John Abatzoglou, Professor of Climatology at the University of California Merced.

“While Southern California is no stranger to high impact wildfires, the impact of these fires and the timing of these fires in the core of what should be the wet season differentiate this event as an extreme outlier.”

California needs better early warning and evacuation systems

The simultaneous occurrence of two major fires, driven by hurricane-force Santa Ana winds into urban areas, created chaotic and unpredictable conditions that overwhelmed more than 300 predeployed firefighters, the study highlights.

Improving the water system's ability to support large-scale firefighting efforts and making sure homes in high-risk zones adhere to defensible space buffer zone requirements will help to reduce the risk of repeat disasters, the researchers say.

They also emphasise the importance of early warning and evacuation systems as 17 of the 28 deaths occurred in West Altadena, a neighbourhood where warnings were delayed compared to other affected areas.

“These fires have highlighted just how vulnerable California is to winter wildfires, underscoring the need for better preparation for a more dangerous future,” said Roop Singh, Head of Urban and Attribution at the Red Cross Red Crescent Climate Centre.