Following last year’s wet winter season in the Southland that resulted in abundant grass and brush, 2024 brought a record-hot summer and now a record-dry start to this year’s rainy season, along with tinder-dry vegetation that has since burned in a series of damaging wildfires, according to research announced Thursday by UCLA.
After years of severe drought, dozens of atmospheric rivers deluged California with record-breaking precipitation in the winter of 2022-23, burying mountain towns in snow, flooding valleys with rain and snow melt, and setting off hundreds of landslides.
This back-and-forth is just the most recent example of the kind of “hydroclimate whiplash” — rapid swings between intensely wet and dangerously dry weather — that is increasing worldwide, according to a paper published Thursday in Nature Reviews.
“The evidence shows that hydroclimate whiplash has already increased due to global warming, and further warming will bring about even larger increases,” lead author Daniel Swain, a climate scientist with UCLA and UC Agriculture and Natural Resources, said in a statement.
“This whiplash sequence in California has increased fire risk twofold: first, by greatly increasing the growth of flammable grass and brush in the months leading up to fire season, and then by drying it out to exceptionally high levels with the extreme dryness and warmth that followed.”
According to the study, global weather records show hydroclimate whiplash has swelled globally by 31% to 66% since the mid-20th century, the international team of climate researchers found — even more than climate models suggest should have happened.
Climate change means the rate of increase is speeding up. The same potentially conservative climate models project that the whiplash will more than double if global temperatures rise 3 degrees Celsius above pre-industrial levels. The world is already poised to blast past the Paris Agreement’s targeted limit of 1.5 C. The researchers synthesized hundreds of previous scientific papers for the review, layering their own analysis on top, researchers said.
Anthropogenic climate change is the culprit behind the accelerating whiplash, and a key driver is the “expanding atmospheric sponge” — the growing ability of the atmosphere to evaporate, absorb and release 7% more water for every degree Celsius the planet warms, researchers said.
“The problem is that the sponge grows exponentially, like compound interest in a bank,” Swain said. “The rate of expansion increases with each fraction of a degree of warming.”