Wild swings in weather from extreme drought to extremely heavy downpours of rain are becoming more common thanks to climate change, new research has shown.
The likelihood has increased by up to 1% per year, and is happening around the world, the researchers warn.
They say ‘feedback loops’ from the land are boosting the trend – and that it may make it harder for societies to respond to natural disasters.
The trend is getting worse in eastern North America, Europe, East Asia, Southeast Asia, southern Australia, southern Africa, and southern South America.
Zong-Liang Yang, a professor at The University of Texas at Austin Jackson School of Geosciences, said: "We are especially concerned with the sudden shift from drought to flood.
"Society usually has difficulty responding to one kind of natural disaster like drought, but now you suddenly have floods, too. And this has been happening in many places."
The study was published in the journal Communications Earth & Environment.
The team looked at three global sets of meteorological and hydrological data from 1980 to 2020.
They found that the likelihood of a sudden shift from drought to dangerous downpours increased roughly a 0.25% to 1% per year over that time period, depending on the location.
There have been many examples of the sudden shift from severe drought to heavy and potentially dangerous downpours in recent years.
For example, in December 2022, California was facing its worst drought in a millennium, but this situation was quickly shifted by heavy rains that caused record flooding in January, February and March this year.
Researchers discovered the land-based feedback loops with the relatively new technique of causality analysis, a statistical technique that can help determine if one factor is directly responsible for another happening.
They found that during heavy drought in humid regions, evaporation of water from soil and plants is kicked into overdrive, pushing precipitation into the air and providing a moisture source for heavy rainfall to develop.
During heavy drought in arid regions, the hot weather and low pressure creates a pressure gradient that draws in moisture from other areas, such as the ocean.
Co-author Shuo Wang, an associate professor at The Hong Kong Polytechnic University, said such rapid shifts are expected to become more likely with climate change.
Wang said, "Climate change is fueling back-to-back droughts and floods which have caused widespread devastation, resulting in loss of life and damages to property, infrastructure, and the environment.
"Our findings provide insights into the development of early warning systems for mitigating the impacts of rapid dry-wet transitions."
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