January 28, 2025

expert reaction to report by World Weather Attribution looking at climate change attribution of the LA wildfires

A report by by the World Weather Attribution (WWA) looks at climate change and the likelihood of wildfire disaster in LA. 

Prof Gabi Hegerl FRS, Professor of Climate System Science, University of Edinburgh, said:

“Given the short timeline that WWA aims for this is a very thorough analysis of the role of climate change and also El Nino conditions contributing to the fires in Los Angeles.  The authors determine several factors that have contributed to this disaster, from severely dry conditions to high fire weather indices, late arrival of winter rains etc.  Several of these factors point to high fire risk, both due to El Nino conditions and global warming.  Overall the paper finds that climate change has made the Los Angeles fires more likely despite some statistical uncertainty.  This is a carefully researched result that should be taken seriously.  El Ninos come and go, but as long as the climate warms we will continue to see increasing risk of this hazard.  Adapting to it will help, and the authors make some suggestions, but this example is one of many of how climate change increases the risk of deadly and costly disasters.”

Dr Karsten Haustein, Climate Scientist, Leipzig University, said:

“I remember a stark and dire warning of an US-based weather forecaster just before the fires.  Sadly, he was absolutely spot on.  The extremely hazardous mix of dry and windy conditions led to unprecedented destruction, displacing tens of thousands of people and costing billions of dollars.  Naturally, folks want to know what role climate change played in this catastrophic disaster.

“Following two very rapid attribution studies by teams from UCLA (California) and IPSL-CNRS (France), now WWA has released their comprehensive rapid attribution study.  The former two have already highlighted that climate change did play a role and made the fires more likely.  Especially the so-called ‘hydroclimate whiplash’, where wetter than average years are followed by drier than average years, contributed to the devastating outcome.  While these year-to-year variations are normal given the strong ENSO teleconnection in the region (El Niño leads to wetter conditions and vice versa for La Niña), now wet gets wetter and dry gets drier for longer.

“Hence one of the key messages of the WWA study is that the dry season in the region lasts longer than it used to be (23 days), increasing the risk for very dry conditions to overlap with strong (St Ana) winds, which occur mainly in winter.  While WWA does not find increasing wind speeds during St Ana events, they do find that the risk for such a dry season has already increased by 35%, with a 6% increase in fire intensity.

“WWA highlights that a more in-depth analysis is required to make conclusive statements about changes in atmospheric circulation that favour such cut-off lows.  But the thermodynamic climate change fingerprint (drier and warmer) is clearly present.  So is the problem of exposure in the region.  Houses are not build to withstand fire.  Instead, they are fuelling the fires.  A tinderbox when combined with built up vegetation from the preceding two wet seasons.  All these aspects are meticulously discussed in WWA’s new attribution study.

“Their press release accurately summarises the scientific findings.  The team involved was larger than ever, including the UCLA colleagues mentioned above.  All methods used to conduct the analysis are peer-reviewed.  The results do confirm prior research such as, for example, the hypothesised ‘hydroclimate whiplash’.  The team also mentions the deficits of global climate models to simulate such wind events, which is why no attribution statement regarding the frequency of occurrence or magnitude of the St Ana winds is made.”

‘Climate change increased the likelihood of wildfire disaster in highly exposed Los Angeles area’ by Clair Barnes et al. was published by World Weather Attribution at 22:00 UK time on Tuesday 28 January 2025. 

Declared interests

Prof Gabi Hegerl: “No competing interests, occasional collaboration with some of the study’s authors.”

Dr Karsten Haustein: “No conflict of interests.”