How Climate Change Impacted the California Wildfires

Rising global temperatures and a prolonged ‘dry season’ may have increased the likelihood and intensity of the California wildfires, study finds.

In January 2025, a series of 14 devastating wildfires broke out in California. The fires lasted from January 7th to January 31st, destroying thousands of buildings, including schools, stores, and homes. Additionally, the fires tragically claimed the lives of at least 29 people, and families who lost their homes are still recovering from this terrible disaster. 

On January 28th, a few days before the fires were contained, a study was published by World Weather Attribution (WWA) that found that global warming was partially responsible for these fires and the tragic losses that came with them. World Weather Attribution is an initiative founded in 2014 that works to publish rapid studies seeking to understand how climate change has impacted recent natural disasters. The initiative is made up of researchers from a variety of institutions. 

The study attributed a 35% increase in the likelihood of fire-prone conditions to climate change and found that the fires were 6% more intense as a result. The report on the California wildfires is not yet peer reviewed, since it’s a process that can often take months. However, WWAs previous studies on heat waves, wildfires, and hurricanes have consistently passed peer review and have been published in reputable academic journals. 

In order to reach these numbers, the researchers analyzed existing climate and weather models to determine how climate change impacts the likelihood of “fire weather” (the conditions that lead to a higher likelihood of wildfires). Additionally, they tracked the change over time in a metric called the Fire Weather Index, which tracks temperature, relative humidity, and wind speeds. Together, these factors contribute to an increase in the risk of wildfires breaking out.

A key piece of how global warming impacted the likelihood of the wildfires is found in the Santa Ana winds. The Santa Ana winds are naturally occurring gusts of wind that return annually and are made possible by the geography of the Western U.S.. They return between fall and spring and can often be extremely strong—this year’s Santa Ana winds reached speeds close to those of a hurricane’s. 

The extremely strong Santa Ana winds, which occurred this year, were responsible for exacerbating and spreading the fires as well as making them extremely difficult to contain. While climate change is not responsible for these extreme winds, it is responsible for how the other factors of fire weather, which come with every dry season, coincided with these winds.

(Photograph: The Atlantic)

The Santa Ana winds exacerbated the Palisades wildfire, causing its initial spread and making it more difficult to contain.

The same study by WWA found that since the Industrial Revolution, California’s annual dry season has increased by an average of 23 days. With every dry season comes a lot of available fuel for wildfires, and global warming is increasing the length of time that these conditions occur annually. This increase in the length of California’s dry season means that there’s a significantly higher risk of the Santa Ana winds overlapping with it, creating conditions that make it likely for wildfires to start and spread quickly.

“This was a perfect storm when it comes to conditions for fire disasters—the ingredients in terms of the climate enabling, the weather driving the fires, and the huge built environment right downwind from where these ignitions occurred,” UC Professor of Climatology John Abatzoglou told reporters at a news conference. Abatzoglou is one of the various scholars who contributed to the report.

Other studies have examined the connection between wildfires and climate change as well.

In 2021, the Proceedings of the National Academy of Sciences (PNAS) published a research article that similarly quantified the growing likelihood of fire weather (indicated by vapor pressure deficit — VPD) due to climate change from 1979 to 2020. VPD illustrates the difference between the actual and potential moisture in the air and is an indicator of aridity. VPD is regularly used as a tool to estimate the risk of wildfires, and in the western U.S., the average VPD is increasing.

In this study, the researchers’ observation-based estimates suggested that around one-third of the increase in VPD could be attributed to the natural variability of weather patterns, something which happens regardless of human activity. However, they attributed the other two-thirds of the increase in VPD to anthropogenic climate change.

This means that not only has climate change been widening the window for more extreme wildfires in California (due to the dry season’s increasing overlap with the Santa Ana winds), but it’s also responsible for the conditions that lead to wildfires becoming more extreme.

The exact amount that any given wildfire’s severity or likelihood has been impacted by climate change is highly variable. While the conditions that led to the California wildfires were made approximately 35% more likely (according to WWA), other fires in previous years have been impacted at varying degrees by climate change.The science journal Nature published an article in 2023 examining how much previous wildfires in California had been affected by climate change. They found that the impact climate change has on any given wildfire is considerably different and varies a lot on a “fire-by-fire and day-by-day basis."

So far, they estimated that climate change has increased the “aggregate expected frequency of extreme daily wildfire growth by 25%” on average in comparison to conditions prior to industrialization. However, some fires fell far outside this average. For some, there was little to no change, and for others, the increase was as high as 461%.

The conditions that led to the fire were uniquely well-tailored to producing the terribly devastating result that was the California wildfires. Unfortunately, WWA’s report also noted that the conditions that led to January’s California wildfires are likely to recur every 17 years in today’s climate. Before we started burning fossil fuels, they would have likely occurred every 23 years, meaning these disasters could possibly be occurring six years more frequently than they would have before the Industrial Revolution.

Ultimately, WWA’s report found that while climate change certainly played a role in the fires, it was not the sole cause. Other factors such as California’s wildfire-prone brush (which have evolved to burn easily and with regularity), the increased amount of people living in the area (which means a higher likelihood of fires caused by cigarettes, fireworks, vehicles, or powerlines), and an increase in the development of new neighborhoods in areas susceptible to wildfires.

More research is certainly needed on just how much climate change will play a role in future wildfires, but WWA’s study clearly shows that we need to do something about climate change or we will risk similar disasters in the years to come.