California wildfires: Why ‘hydroclimate whiplash’ to blame for deadly blaze

LOS ANGELES — Imagine that your city experiences its worst drought in decades, only to be suddenly inundated by record-breaking rainfall weeks later. This dramatic swing between weather extremes, known as “hydroclimate whiplash,” is becoming increasingly common worldwide – and new research suggests it’s getting worse due to climate change.

Published in Nature Reviews Earth & Environment, the report reveals that these rapid transitions between very wet and very dry conditions have increased by 31-66% globally at seasonal timescales since the mid-twentieth century. Even more concerning, with continued warming, these weather whiplashes are projected to increase by a staggering 113% over land areas if global temperatures rise by 3°C.

Los Angeles provides a timely example of this phenomenon. After experiencing two extremely wet winters that produced abundant grass and brush growth, 2024 brought a record-hot summer followed by an extraordinarily dry start to the 2025 rainy season. The result? Tinder-dry vegetation that has fueled a series of devastating wildfires.

“The evidence shows that hydroclimate whiplash has already increased due to global warming, and further warming will bring about even larger increases,” says lead author Daniel Swain, a climate scientist with UCLA and UC Agriculture and Natural Resources, 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.”

The science behind these intensifying weather swings is rooted in what researchers call the “expanding atmospheric sponge” effect. As the atmosphere warms, it can hold and process more water – approximately 7% more for each degree Celsius of warming. “The problem is that the sponge grows exponentially, like compound interest in a bank,” Swain explains. “The rate of expansion increases with each fraction of a degree of warming.”

This increased capacity works both ways: when conditions are right for rain, there’s more moisture available for extreme precipitation events. When conditions are dry, the warmer atmosphere’s increased “thirst” can more rapidly pull moisture from soil and vegetation.

Many previous studies have focused solely on precipitation patterns while overlooking the atmosphere’s growing evaporative demand. This thirstier atmosphere pulls more water from plants and soil, making drought conditions worse beyond just the lack of rainfall.

The impacts of these weather whiplashes extend far beyond immediate flooding or drought damage. Rapid transitions between extreme wet and dry conditions can trigger a cascade of secondary disasters: harmful algal blooms in water bodies, increased wildfire risk from vegetation growth followed by rapid drying, and disease outbreaks as changing conditions create favorable environments for pathogens.

“Hydroclimate in California is reliably unreliable,” says co-author John Abatzoglou, a UC Merced climate scientist. “However, swings like we saw a couple years ago, going from one of the driest three-year periods in a century to the once-in-a-lifetime spring 2023 snowpack, both tested our water-infrastructure systems and furthered conversations about floodwater management to ensure future water security in an increasingly variable hydroclimate.”

The study’s authors found that these effects are not distributed evenly across the globe. The largest increases in weather whiplash are projected for high latitudes (especially northern Eurasia and Canada) and a broad swath extending from northern Africa across the Arabian Peninsula into South Asia. These regions face potentially devastating impacts on agriculture, water resources, and infrastructure.

While climate change hasn’t necessarily increased the likelihood of specific wind events in places like Southern California, it has increased the overlap between extremely dry vegetation conditions and the occurrence of these wind events – creating perfect conditions for destructive wildfires.

The research suggests that reducing global warming could directly slow or reduce the increase in weather whiplash. However, with the world currently on track for 2-3 degrees Celsius of warming this century, substantial increases in these extreme transitions are likely, requiring careful consideration in risk assessments and adaptation planning.