Los Angeles is on fire, with accelerating hydroclimate whiplash playing a significant role in the climate dynamics.
After enduring prolonged drought, California experienced an onslaught of atmospheric rivers that delivered record rainfall during the winter of 2022-23. This resulted in mountain towns being buried under snow, valley flooding from rain and snowmelt, and hundreds of landslides.
Following a second very wet winter in the southern regions, which led to a surge of grass and brush growth, 2024 ushered in a record-breaking hot summer and an unusually dry beginning to the 2025 rainy season. This left behind dry vegetation that was ultimately consumed by a series of devastating wildfires.
This situation illustrates the phenomenon of “hydroclimate whiplash”—rapid shifts between heavy rainfall and extreme dryness—that is becoming more common around the globe, as discussed in a recent paper published in Nature Reviews.
“Our findings indicate that hydroclimate whiplash has already escalated due to global warming, and further increases are likely as temperatures continue to rise,” stated lead author Daniel Swain, a climate scientist affiliated with UCLA and UC Agriculture and Natural Resources. “California’s experience of whiplash has doubled the fire risk: first, by significantly boosting the growth of flammable vegetation before the fire season, and then by drying it out excessively due to the subsequent extreme dryness and heat.”
Analysis of global weather data shows that hydroclimate whiplash has surged by 31% to 66% worldwide since the mid-20th century, surpassing expectations set by climate models. The speed of this increase is accelerating due to climate change. Conservative climate predictions indicate that whiplash could more than double if global temperatures rise by 3 degrees Celsius over pre-industrial levels. Given the current trajectory, the world will likely exceed the Paris Agreement’s goal of limiting warming to 1.5°C. The researchers compiled insights from hundreds of prior studies to support their review.
Human activities contributing to climate change are the primary cause of the rapid whiplash, largely driven by the “expanding atmospheric sponge”—the atmosphere’s increasing capacity to evaporate, hold, and release 7% more water for every degree Celsius of warming, as noted by researchers.
“This issue resembles compound interest in a bank, with the sponge expanding exponentially,” explained Swain. “The rate of expansion accelerates with each fraction of a degree of warming.”
The global impacts of hydroclimate whiplash extend beyond just floods and droughts; they include increased risks of oscillating between the two extremes. This results in cycles of over-watered then dehydrated vegetation, alongside landslides on saturated hillsides where recent wildfires have stripped away soil-retaining plants. Swain emphasized that warming intensifies the destructive potential of these transitions.
Many earlier studies focused mainly on precipitation without considering the heightened demand for evaporation. The thirstier atmosphere siphons more water from plants and soil, worsening drought conditions beyond mere rainfall shortages.
“The expanding atmospheric sponge effect may provide a cohesive explanation for some of the most striking and alarming impacts of climate change that have seemingly intensified recently,” Swain remarked. “While the planet’s warming has been relatively steady, there’s been a growing focus on accelerating climate impacts over the past 5 to 10 years. The rise in hydroclimate whiplash, driven by this exponentially expanding atmospheric sponge, might offer a convincing rationale.”
This acceleration, coupled with the expected upswings in fluctuating water cycles, has significant implications for how we manage water resources.
“It’s crucial not to solely focus on either extreme rainfall or extreme droughts, as we must effectively handle these increasingly significant water influxes, while also bracing for drier periods,” Swain stated. “This highlights the importance of ‘co-management’ as a key strategy, leading to more comprehensive insights about the most suitable interventions and solutions, rather than viewing droughts and floods in isolation.”
Traditionally, water management strategies have either redirected floodwaters quickly into the ocean or employed slower methods like letting rain seep into groundwater. However, when considered independently, each approach leaves cities susceptible to the other extreme of climate whiplash, the researchers cautioned.
“Hydroclimate patterns in California are inconsistently reliable,” commented co-author John Abatzoglou, a climate scientist at UC Merced. “The swings we experienced recently—transitioning from one of the driest three-year spans in a century to an exceptional spring 2023 snowpack—have both tested our water infrastructure and sparked discussions about managing floodwaters, ensuring future water security in an increasingly variable climate.”
Regions likely to be most affected by hydroclimate whiplash include northern Africa, the Middle East, South Asia, northern Eurasia, and the tropical Pacific and Atlantic, although impacts will also be felt in many other areas.
“The rise in hydroclimate whiplash may become one of the more widespread changes experienced on a warming planet,” Swain noted.
This week in California, despite winds fueling severe wildfires, it’s the rainfall deficit driven by whiplash that has entrenched Southern California in fire season.
“Current evidence does not strongly indicate that climate change has altered the severity or frequency of wind events in Southern California,” Swain said. “However, climate change does enhance the likelihood of extremely dry vegetation coinciding with these wind occurrences. This ultimately forms the critical climate link to the wildfires in Southern California.”
Under high warming scenarios, California is expected to experience an increase in both extremely wet and extremely dry years and seasons later this century.
“Less warming corresponds to a lower increase in hydroclimate whiplash,” Swain noted. “Consequently, any measures that reduce warming due to climate change will directly mitigate or decrease the rise in whiplash. Unfortunately, we remain on track to see between 2 and 3 degrees Celsius of warming this century—indicating that significant increases in whiplash are forthcoming. It’s essential we factor this into our risk assessments and adaptation strategies.”
This research received support from The Nature Conservancy of California and the Swiss National Science Foundation.
Key takeaways
- Hydroclimate whiplash—rapid fluctuations between severe wet and dry conditions—has risen globally due to climate change, with further substantial rises anticipated as temperatures continue to climb, as highlighted by a research team led by UCLA’s Daniel Swain.
- The “expanding atmospheric sponge,” referring to the atmosphere’s capacity to evaporate, absorb, and release 7% more water for every degree Celsius increase in global temperature, is a major factor in the whiplash phenomenon.
- Efficient management of extreme rainfall and drought requires a comprehensive approach rather than treating each event separately, as researchers emphasized.
