New evidence links climate change to California’s worsening wildfire seasons
Wildfires are becoming more frequent, widespread, and severe in the state of California and other regions across the globe.
California has a long history of fires, but as the fires grow in size and severity every year, many continue to question if climate change is to blame.
A new study conducted by researchers from the Earth Institute at Columbia University offers new evidence of how human-driven climate change is worsening California’s wildfire seasons.
The study, published in the journal Earth’s Future, considers many different factors that increase the risk of wildfires, and the researchers analyzed more than 100 years of data.
The researchers found that the large summer fires in recent history have a strong link to drier ground conditions due to increases in temperature. Not only have fires become more frequent and widespread over the years, but wildfires could get exponentially worse in the next 40 years.
“The ability of dry fuels to promote large fires is non-linear, which has allowed warming to become increasingly impactful,” the researchers wrote in the study. “Human-caused warming has already significantly enhanced wildfire activity in California, particularly in the forests of the Sierra Nevada and the North Coast, and will likely continue to do so in the coming decades.”
In California, summer temperatures have risen 3.25 degrees Fahrenheit since 1896, but it wasn’t until the early 1970s that temperatures started to really climb.
With this increase in summer averages, there was also an increase in fires which covered a wider area. From 1972 to 2018, there was a fivefold increase in area burned during summer fires and an eightfold increase in summer forest fires in general.
The warmer temperatures sucked out more moisture from the soil and vegetation, making trees and plants more likely to burn during a fire and allowing fires to spread farther and faster.
The process of warmer air drawing moisture from the ground is called vapor pressure deficit.
The researchers discovered that vapor pressure deficit due to rising temperatures played a significant role in the increase in forest fires from 1972 to 2018 in some areas of California.
Other factors like the seasonal variation in precipitation and temperature, habitat fragmentation, fire suppression, and growing infrastructure can also influence fire risk, the researchers say.
“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 the Park Williams, the lead author of the study. “We have tried to provide one-stop shopping to show people how climate has or, in some cases, hasn’t affected fire activity.”
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