Climate whiplash helping to fuel California's massive wildfires

• Several studies point to a future with more frequent shifts between wet and dry extremes.
• There is an "increase in this hydro-climate whiplash" and it creates an ideal scenario for worsening wildfires by growing vegetation then burning it, says Daniel Swain, a climate scientist at UCLA.

Driving the news: The Park Fire that began in Butte County in northern California has burned more than 397,000 acres, making it the fourth-largest fire in California's history. Authorities say they think the fire began from an act of arson.

• CalFire says 95% of wildfires are caused by people.

How it happened: Most of California wasn't in a drought at the start of the fire season.

• The majority of its reservoirs were above their average level from a wet winter punctuating back-to-back years with significant rainfall that broke 25-year records in some places.
• This wet period followed an extreme, two-decade-long drought that exceeded the severity of any observed for more than a millennia.
• The wet winter spurred the growth of fast-growing shrubs and grasses.

Then one of the hottest springs in recent history turned into one of the hottest summers on record.

• An extreme, long-lasting heat wave that stretched from June into July extracted "a tremendous amount of water" out of the soil and plants, especially those at lower elevations, "drying it out to the point of it being a kiln," Swain says.
• The sustained heat and extraction of moisture from the landscape is an "unprecedented combination of conditions," he says.
• "It's a combination that seems incongruous," Swain says. But it is also one that "we're starting to see as thirstiness of atmosphere increases with warming."
• Many locations in California had their warmest July on record, for example, with some setting milestones for their warmest month of any month in history.

How it works: As Earth's atmosphere warms from human-caused climate change, it can evaporate and carry more water, producing more intense rains that fuel the growth of vegetation.

• At the same time, decades of suppressing natural fires and cultural burning in some places has allowed for unchecked plant growth and dense forests, experts tell Axios.
• "The natural fire deficit is the problem" because it results in denser fuel, Swain says. "Then climate change comes along and kiln dries that extra fuel."

Flashback: There are indications of climate whiplash and its relationship to fire in California's past climate.

• Scientists studying an almost 9,000-year-old stalagmite in a cave in California's Santa Cruz mountains saw an increase in markers of fire in the stalagmite's chemistry alongside what they suspect was an increase in climate whiplash.
• "Timing-wise, we think the climate whiplash increase came first and then was followed by probably a change in vegetation above the cave, and then the fire," says Jessica Oster, a paleoclimate researcher and professor at Vanderbilt University.

• The climate whiplash then was "ultimately driven by melting of ice and water flow into the North Atlantic, which is happening right now as well," Oster says. However, now that same dynamic is playing out due to human-driven warming.

The big picture: In California, wildfires have burned more than 750,000 acres, compared to the five-year average of just 141,000 acres, so far this year, and the Park Fire is just one of 89 large fires burning across the West.

• A recent study found the frequency and magnitude of extreme wildfire events more than doubled in the past two decades, Axios' Andrew Freedman reported.
• The area burned by wildfires in the western U.S. has "increased by a factor of four since the 1970s" and is attributable to human-caused climate change, says Mike Flannigan, a professor of wildland fire at Thompson Rivers University in British Columbia.
• "I cannot be any clearer than that."
• A warmer world also means more lightning — a key source of ignition for wildfires in certain ecosystems, Flannigan says. As another heat wave builds across the West, the risk of dry lightning — and new fire starts — is increasing, Swain posted on X.

What to watch: Each wildfire has its distinctive characteristics, including a mix of past fire management practices, vegetation and climate, says Alexandra Syphard, a senior research ecologist at the Conservation Biology Institute.

• "There is no one-size-fits-all prediction for fire futures in California or a single strategy to mitigate fire risk to people, infrastructure, and ecosystem resilience," Syphard and her colleagues write in a paper published on Monday in the journal PNAS.

Editor's note: This story has been updated to reflect the Park Fire has grown to the fourth largest fire in California's history.