Climate change is the leading cause of wildfires in the US.

TO study published by the procedures of the National Academy of Sciences (PNAS) found that climate change was the main factor in the increase in wildfires on the US West Coast.

The study sought to analyze the impact of climate change caused by human activity in naturally arid areas impacted by an increase in wildfires, such as California. The researchers found that man-made impact had a 68% to 88% chance of being the determining factor in the atmospheric conditions fueling wildfires, which have increased in frequency and severity.

The researchers tracked the levels of vapor pressure deficit, or VPD, in the air to determine their hypothesis. VPD is defined as the difference between the amount of moisture in the air and the amount of moisture that the air can hold when it is saturated. The greater the deficit, the more moisture the atmosphere absorbs from the soil and plants, preparing the landscape to burn. High levels of VPD mean that a specific climate is more prone to starting fires.

The increase in VPD has been well documented in scientific circles, although until now it was not clear why the levels had risen to current levels. The results showed that for the period 1979 to 2020, the variation in atmospheric circulation showed that, on average, only 32% of the observed VPD was maintained during the warm season (May to September), which means that 68% remaining of the upward trend in VPD is likely due to human-caused climate change.

Researchers who co-authored the study told the Los Angeles Times that they did not expect human-caused climate change to outpace natural climate variability as the main contributor to fire weather until about 2080.

“Before 2000, we can explain this fire climate pretty well just using weather patterns,” Rong Fu, a UCLA-based climate researcher and co-author of the study, told the LA Times. “Now we can only explain about 30% of what we see with fire weather.”

The prevalence of wildfires has grown at a worrying rate: Wildfires have burned an average of 5,200 square miles of land per year in the western US From 2001 to 2018, nearly double the area burned by comparison. with the period from 1984 to 2000, and they have become more significant in stature. The August 2020 Complex Fire damaged more than a million acres of land and claimed the life of a firefighter on its way to becoming the largest wildfire event in California history.

A wildfire burns in the Angeles National Forest during the Bobcat Fire in Los Angeles, California, USA, September 17, 2020 (Credit: REUTERS / RINGO CHIU)

The worrying trend appears to be getting worse before improving. This year alone, California reported its hottest summer on record, the driest in nearly a century, and its second-largest wildfire – the Dixie Fire, which claimed more than 960,000 acres of land in Northern California.

The role of climate change in wildfires is a key part of the agenda at the United Nations COP26 conference in Glasgow, Scotland, where dozens of world leaders meet to set new emission reduction targets.

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