California's experience illustrates the increasing risks. Following years of intense drought, the winter of 2022-23 brought an unprecedented series of atmospheric rivers, unleashing torrential rain and heavy snow. These events caused flooding, landslides, and widespread damage. The subsequent wet winter further fueled the growth of vegetation, which dried out during the record-hot summer of 2024, creating ideal conditions for wildfires as the 2025 rainy season begins with exceptional dryness.
"The evidence shows that hydroclimate whiplash has already increased due to global warming, and further warming will bring about even larger increases," said Daniel Swain, lead author and 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."
Globally, hydroclimate whiplash events have risen by 31% to 66% since the mid-20th century, according to the study published in Nature Reviews. The increase surpasses projections from climate models, with further escalation likely if global temperatures rise by 3 degrees Celsius above pre-industrial levels. The analysis synthesized hundreds of scientific papers and included new data layers to deepen understanding.
Researchers identified anthropogenic climate change as the main driver behind the expanding phenomenon, with a key factor being the "expanding atmospheric sponge." This refers to the atmosphere's enhanced capacity to absorb and release water, which grows by 7% with each degree Celsius of warming.
"The problem is that the sponge grows exponentially, like compound interest in a bank," Swain explained. "The rate of expansion increases with each fraction of a degree of warming."
The impacts of hydroclimate whiplash extend far beyond California, causing floods, droughts, and other extremes globally. Rapid shifts between wet and dry conditions can also trigger landslides and a cycle of vegetation growth followed by combustion, exacerbating wildfire risks. Researchers noted that even slight increases in global temperatures amplify these destructive transitions.
Previous studies often focused solely on precipitation, overlooking the role of evaporative demand. As Swain explained, "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."
The phenomenon poses major challenges 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. A co-management approach that integrates both drought and flood mitigation is crucial.
Traditional methods, such as quickly diverting floodwaters to the ocean or slowly replenishing aquifers, may not address the dual challenges posed by hydroclimate whiplash. This was evident in California's recent extreme events, said John Abatzoglou, a UC Merced climate scientist and study co-author. "Hydroclimate in California is reliably unreliable," he noted, highlighting the strain placed on water infrastructure and the ongoing need for innovative floodwater management strategies.
Regions most affected by increasing hydroclimate whiplash include northern Africa, the Middle East, South Asia, northern Eurasia, and parts of the tropical Pacific and Atlantic. However, the impacts will be felt globally.
"Increasing hydroclimate whiplash may turn out to be one of the more universal global changes on a warming Earth," Swain said.
In Southern California, the link between climate change and wildfires is evident. While there's little evidence that climate change influences wind events that spread fires, it has increased the overlap between dry vegetation conditions and these wind events, Swain explained. "This, ultimately, is the key climate change connection to Southern California wildfires."
Reducing global warming could mitigate the projected increase in hydroclimate whiplash, but current trajectories suggest significant risks remain. "The less warming there is, the less of an increase in hydroclimate whiplash we're going to see," Swain said. "Yet we are currently still on a path to experience between 2 degrees and 3 degrees Celsius of global warming this century - so substantial further increases in whiplash are likely in our future, and we really need to be accounting for this in risk assessments and adaptation activities."
Related Links
University of California - Los Angeles
Climate Science News - Modeling, Mitigation Adaptation
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