New research this week provides fresh evidence about the connection between climate change and wildfires, specifically in California, where experts say global warming is a key factor in the state’s deadly and increasingly devastating fire seasons.

The findings coincide with an already-vicious wildfire season in parts of North America, including on the West Coast and in parts of Canada. One state garnering particular attention is Alaska, where a major heat wave has been linked to many of the fires that have hit the state this year.

A new study in the American Geophysical Union’s Earth Future journal closely inspects the factors that can lead to wildfires, ultimately concluding that a “warming climate” is a decisive driver in many cases. That trend is particularly true in the North Coast and Sierra Nevada regions in California — the main area the study focuses on — where brutal wildfires last year completely destroyed entire towns, in addition to killing dozens of people and costing over $3 billion in damages.

The study looks closely at rising temperatures in California, which has experienced an uptick of 1.80 degrees Celsius (3.25 degrees Fahrenheit) since 1896, most of that since the 1970s. Wildfires are a naturally occurring phenomenon and common to that wooded area, especially during warm weather when moisture evaporates from vegetation and dries out soil. But with temperatures spiking at record rates, the study notes, the already-active fire season is becoming more and more severe.

Area burned by California wildfires in thousands of square kilometers, 1972-2018. Specific regions studied are at upper left. (Credit: Williams et al., 2019.)

“It’s not a surprise to see that climate has this effect in forests, but California is so big and so variable, there is no one-size-fits-all explanation for how climate might affect wildfires across the board,” said Park Williams, a bioclimatologist and the study’s lead author. “We have tried to provide one-stop shopping to show people how climate has or, in some cases, hasn’t affected fire activity.”

Other factors are also at play in exacerbating wildfires in California, including the encroachment of human infrastructure into forests. That’s on top of efforts to suppress naturally-occurring fires, which have lead to a build-up of “flammable materials” in fire-prone areas, the study notes. When coupled with warming temperatures, these factors combine to exacerbate damage, sparking fires more easily and putting more people at risk.


The study’s findings build on prior research about the link between climate change and worsening wildfires. Another 2016 study by Williams and his colleagues found that climate change has doubled forest fires in the western United States since 1984. And the new study found that as temperatures continue to rise, wildfires could see a staggering uptick in the next 40 years.

Meanwhile, wildfire season is already taking a toll in several areas, with warming temperatures seen as the culprit. Global warming is thawing tundra in the far north, exposing many areas and drying out forests. That scenario has proven a major breeding ground for fires, with more than 1.2 million acres already scorched in Alaska this year. The state, which typically isn’t used to high summer heat, has been experiencing a severe heat wave, with temperatures reaching 90 degrees Fahrenheit in the city of Anchorage on July 4 for the first time ever.

Alaska’s climate varies considerably from states like California, but the underlying connection between global warming and more severe wildfires is broadly applicable. The authors of the new study also emphasize that the current fire uptick in California is based on “a relatively small amount of warming” compared to what could come in future years.

“[T]he influence of anthropogenic warming on wildfire activity over the next few decades,” they note, “will likely be larger than the observed influence thus far where fuel abundance is not limiting.”