Flames burn during the McKinney Fire in the Klamath National Forest on July 31, 2022.

David Mcnew | AFP | Getty Images

The area burned from wildfires in California’s northern and central forests increased fivefold from 1971 to 2021, an increase driven largely by human-caused climate change, according to new research published in the Proceedings of the National Academy of Sciences.

The ten largest wildfires in California happened in the last two decades, five of which occurred in 2020 and eight after 2017. And scientists estimate the area burned during an average summer could rise as much as 50% by mid-century as hotter and drier conditions intensify the blazes.

The analysis comes just days after wildfire smoke from Canada traveled to the U.S. East Coast and created hazardous air quality levels in major metro areas like Philadelphia, Washington, D.C., and New York City. 

The researchers conducted a statistical analysis of temperature and wildfire data for summers in California between 1971 and 2021 and assessed models that showed how the last few decades may have looked without human-caused greenhouse gas emissions. They discovered that burned area increased 172% more than it would have without climate change.

“It has become clear that anthropogenic climate change is the major driver of this increase in wildfire damage,” Amir AghaKouchak, a UCI professor of civil and environmental engineering and a co-author of the paper, said in a release.

The researchers identified below-average precipitation, hotter summer temperatures, lower springtime mountain snowpack and more frequent weather extremes as factors connecting climate change and wildfire risk.

Studies have also shown that climate change and variability are responsible for creating dry air and fueling a larger vapor pressure deficit, or the difference between the amount of moisture in the air and how much moisture the air can hold when it’s saturated. Another factor that contributes to fires is poor forest management, which leaves dead wood and undergrowth that help ignite blazes.

“Our paper makes it clear that the problem is ours to fix and that we can take steps to help solve it,” AghaKouchak said. “By acting now to reduce our carbon dioxide emissions and pursue more sustainable transportation, energy production and agricultural practices, we can reduce the adverse effects of global climate change.”

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