California wildfires burn 500% more land because of climate change

By Jordan Evans, CNN and Brandon Miller, CNN Meteorologist
Updated 9:14 AM ET, Wed July 17, 2019

Climate change caused the increase in size of wildfires occurring across California in the last 50 years, according to a new study published in this week's journal Earth's Future.

Since the early 1970s, California wildfires have increased in size by eight times, the study says, and the annual burned area has grown by nearly 500%.

"Human-caused warming has already significantly enhanced wildfire activity in California, particularly in the forests of the Sierra Nevada and North Coast, and will likely continue to do so in the coming decades," the authors of the paper wrote.

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The cause of the increase is simple. Hotter temperatures cause drier land, which causes a parched atmosphere.

"The clearest link between California wildfire and anthropogenic climate change thus far has been via warming-driven increases in atmospheric aridity, which works to dry fuels and promote summer forest fire," said the report.

"It is well established that warming promotes wildfire throughout the western US, particularly in forested regions, by enhancing atmospheric moisture demand and reducing summer soil moisture as snowpack declines."

Williams told CNN that human-caused warming of the planet has caused the vapor pressure deficit to increase by 10% since the late 1800s, meaning that more evaporation is occurring. By 2060, he expects this effect to double.

"This is important because we have already seen a large change in California wildfire activity from the first 10%. Increasing the evaporation has exponential effects on wildfires, so the next 10% increase is likely to have even more potent effects," he said.

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tags: extreme weather, severe weather