Climate “whiplash” between extremely wet and dry conditions, which spurred catastrophic fires in Los Angeles, is increasing exponentially around the world because of global heating, analysis has found.
Climate whiplash is a rapid swing between very wet or dry conditions and can cause far more harm to people than individual extreme events alone. In recent years, whiplash events have been linked to disastrous floods in east Africa, Pakistan and Australia and to worsening heatwaves in Europe and China.
The research found that almost everywhere on the planet has experienced between 31% and 66% more whiplash events since the mid-20th century, as emissions from fossil fuel burning heated the atmosphere. The scientists said whiplash events would rise exponentially as heating continued, more than doubling if the world heats to 3C. Humanity is on track for 2.7C of heating.
The underlying cause for whiplash events is that a warmer atmosphere can hold more water vapour. This means more torrential downpours when it rains but also more intense drought when it is dry, as the thirstier atmosphere sucks up more water from soil and plants. The experts liken the effect to a sponge absorbing water then releasing it when squeezed. As temperature rises, the atmospheric sponge gets larger at an even faster rate.
“The planet is warming at an essentially linear pace, but in the last five or 10 years there has been much discussion around accelerating climate impacts,” said Dr Daniel Swain at the California Institute for Water Resources. “This increase in hydroclimate whiplash, via the exponentially expanding atmospheric sponge, offers a potentially compelling explanation.”
“There is abundant evidence that increasing hydroclimate volatility will likely be a near-universal signature of climate change over global land area,” he said.
Prof Richard Allan, at the University of Reading, UK, and not part of the study team, said: “It is only by rapidly cutting greenhouse gas emissions across all sectors of society that we can limit the increasing severity of hot, dry and wet extremes, including conditions conducive to more potent wildfires.”
The new analysis, published in Nature Reviews Earth and Environment, assessed hundreds of previous studies to determine the trend of whiplash events. The LA fires are the latest example of whiplash, in which years of drought were followed by record-breaking winter rain and snow, leading to abundant grass and brush. Then a record-hot summer in 2024 and record-dry start to the rainy season, dried out the vegetation enabling the terrible wildfires.
In east Africa, drought left 20 million people short of food from 2020 to 2023, then in late 2023 torrential rains destroyed thousands of hectares of crops and displaced more than 2 million people from their homes.
Whiplash events increase the impact of floods, as hard dry ground struggles to absorb heavy rain, and can precipitate landslides, as dry land is suddenly drenched. They can also increase toxic algal blooms in water supplies, when high temperatures follow heavy rain, and cause surges in populations of disease carrying mosquitoes or rats.
“Increasingly rapid and large transitions between extreme wet and dry states are likely to challenge not only water and flood management infrastructure, but also disaster management, emergency response and public health systems that are designed for 20th-century extremes,” the researchers said.
after newsletter promotion
They said the intensifying of cascading extreme weather impacts urgently needed to be incorporated into disaster planning and infrastructure design. For example, allowing rivers to access more of their natural floodplains slows the flow of water during wet periods and helps recharge aquifers for use during dry periods, as does making cities more permeable to rain by reducing the area covered by tarmac and concrete.
“This urgency is especially great in central and northern Africa, the Middle East and south Asia given the triple confluence of large projected increases in whiplash, very high population exposure and underlying socioeconomic factors that increase vulnerability in these regions,” they said.
Dr Kevin Collins, at the Open University, UK, said: “We have to stop thinking and planning as if weather events and climate are predictable and their pattern unchanging. Instead, we need to develop more systemic ways of understanding, planning and living in a climate changing world.”
Sir Brian Hoskins, at Imperial College London, UK, said: “It’s interesting to see the new paper’s findings that climate models likely underestimate the changes seen so far, but even those models suggest a doubling of the volatility for a global temperature warming of 3C – now looking increasingly likely that we’ll reach.”