Hydroclimatic Whiplash: Drought and Flood in Alternation
California is a vivid example of a global phenomenon known as “hydroclimatic whiplash,” which involves sudden and dramatic swings between extreme wet and dry conditions.
These abrupt fluctuations are increasingly destabilising ecosystems and communities, as a new study published in Nature Reviews Earth and Environment reveals.
The study shows how climate change is intensifying these weather patterns and the associated risks — from destructive wildfires to devastating floods.
A State in Constant Flux
The winters of 2022–23 and 2023–24 brought California unprecedented precipitation, fuelled by dozens of atmospheric rivers.
Mountain towns were buried under snow, valleys were flooded by rain and snowmelt, and landslides occurred throughout the state.
However, these floods were followed by record heat in the summer and a drought-dominated start to the 2025 rainy season. The resulting dry vegetation provided ample fuel for a series of wildfires.
“This whiplash sequence in California has increased fire risk in two ways,” explains lead author Daniel Swain, climate scientist at the University of California, Los Angeles (UCLA) and UC Agriculture and Natural Resources.
“First, because the growth of flammable grasses and shrubs increased significantly in the months leading up to the fire season, and second, because the subsequent extreme dryness and heat dried them out to an exceptionally high degree.”
Global Trends in Climate Whiplash
The situation in California reflects a global trend. The study found that hydroclimatic whiplash events have increased by 31% to 66% worldwide since the mid-20th century, exceeding the predictions of climate models.
The trend is accelerating due to human-caused climate change, with projections suggesting that whiplash events could more than double if global temperatures rise three degrees Celsius above pre-industrial levels. The climate crisis continues to intensify.
One key reason for this intensification is the “expanding atmospheric sponge,” a phenomenon in which a warmer atmosphere absorbs and releases more water.
With each degree Celsius of warming, the atmosphere's capacity to store moisture increases by 7%, further amplifying the severity of droughts and floods.
“The problem is that the sponge grows exponentially, like compound interest in a bank,” said Swain. “The rate of expansion increases with every fraction of a degree of warming.”
Beyond Rainfall: The Role of Evaporation
While many studies focus exclusively on precipitation patterns, this study emphasizes the role of increasing evaporative demand.
A warming atmosphere draws more moisture from plants and soils, thereby worsening drought conditions even when precipitation does not decrease.
“The expanding atmospheric sponge effect could provide a unified explanation for some of the visible impacts of climate change,” said Swain.
These include rapid transitions between flooding and drought, landslides triggered by oversaturated soils, and cycles of vegetation growth and fire.
Challenges for Water Management
The intensifying hydroclimatic whiplash poses major challenges for water management.
California's traditional strategies, such as diverting floodwater into the ocean, must be balanced with measures to retain water for prolonged dry periods. Swain emphasized the importance of a “co-management” approach that addresses drought and flood risks jointly.
John Abatzoglou, climate scientist at UC Merced and co-author of the study, pointed to the strain on California's infrastructure:
«The water climate in California is reliably unreliable. Fluctuations like those we experienced a few years ago, from one of the driest three-year periods in a century to the exceptional snowpack of spring 2023, have both stressed our water infrastructure systems and spurred conversations about flood management to ensure future water security in an increasingly variable hydroclimate.»
Global Phenomenon of Climate Whiplash
While California is an extreme example, hydroclimatic whiplash is a global problem.
The most dramatic increases are projected for regions such as North Africa, South Asia, and the tropical Pacific, but almost all regions will face growing risks.
«The increasing hydroclimatic whiplash could prove to be one of the universal global changes on a warming Earth,» says Swain.
The risk of wildfires in Southern California has been further heightened by the absence of rain and the dry vegetation left over from earlier wet periods.
While seasonal winds such as the Santa Anas play a role in the spread of fires, Swain noted that «climate change amplifies the overlap between extremely dry vegetation conditions later in the season and the occurrence of these wind events.»
«This is ultimately the most important link between climate change and wildfires in Southern California.»
Urgent Need to Reduce Warming
The study underscores the urgent need to reduce global warming in order to slow the intensification of hydroclimatic whiplash.
«The less warming there is, the smaller the increase in hydroclimatic whiplash,» says Swain. However, as the planet is set to warm by two to three degrees Celsius this century, a significant increase in variability is likely.
Adapting to these changes requires a rethinking of water management, infrastructure, and water conservation strategies. By accounting for both ends of the water spectrum — flooding and drought — policymakers and communities can better prepare for the challenges of a warming world. More on the impacts on Environment and Conservation.
