Hydroclimate whiplash in California: 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.
Following a second extremely wet winter in southern parts of the state, resulting in abundant grass and brush, 2024 brought a record-hot summer and now a record-dry start to the 2025 rainy season, along with tinder-dry vegetation that has since burned in a series of damaging wildfires.
This 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 today 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,” said lead author Daniel Swain, a climate scientist with UCLA and UC Agriculture and Natural Resources. “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.”
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.
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.”
The global consequences of hydroclimate whiplash include not only floods and droughts, but the heightened danger of whipsawing between the two, including the bloom-and-burn cycle of overwatered then overdried brush, and landslides on oversaturated hillsides where recent fires removed plants with roots to knit the soil and slurp up rainfall. Every fraction of a degree of warming speeds the growing destructive power of the transitions, Swain said.
Many previous studies of climate whiplash have only considered the precipitation side of the equation, and not the growing evaporative demand. The thirstier atmosphere pulls more water out of plants and soil, exacerbating drought conditions beyond simple lack of rainfall.
“The expanding atmospheric sponge effect may offer a unifying explanation for some of the most visible, visceral impacts of climate change that recently seem to have accelerated,” Swain said. “The planet is warming at an essentially linear pace, but in the last 5 or 10 years there has been much discussion around accelerating climate impacts. This increase in hydroclimate whiplash, via the exponentially expanding atmospheric sponge, offers a potentially compelling explanation.”
That acceleration, and the anticipated increase in boom-and-bust water cycles, has important implications for water management.
“We can’t look at just extreme rainfall or extreme droughts alone, because we have to safely manage these increasingly enormous influxes of water, while also preparing for progressively drier interludes,” Swain said. “That’s why ‘co-management’ is an important paradigm. It leads you to more holistic conclusions about which interventions and solutions are most appropriate, compared to considering drought and flood risk in isolation.”
In many regions, traditional management designs include shunting flood waters to flow quickly into the ocean, or slower solutions like allowing rain to percolate into the water table. However, taken alone, each option leaves cities vulnerable to the other side of climate whiplash, the researchers noted.
“Hydroclimate wiplash in California is reliably unreliable,” said co-author John Abatzoglou, a UC Merced climate scientist.
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