Flash droughts are becoming more frequent due to climate change, and this trend is only likely to worsen, according to a study published in Science. A team of researchers from the University of Southampton, UK, showed that flash droughts that develop rapidly are ‘the new normal’ for droughts, which makes preparing for their impact more difficult.
Droughts take months to develop, but flash droughts can develop in a matter of weeks. These droughts are caused by extremely low levels of rain combined with high evaporation, quickly removing water from the soil. They can establish very quickly but then last for months, damaging vegetation and triggering heat waves and wildfires.
A team of researchers from the University of Southampton wanted to assess how these quick droughts develop under different carbon emission scenarios. “Climate change has effectively sped up the onset of droughts,” said Professor Justin Sheffield, Professor of Hydrology and Remote Sensing at the University of Southampton and co-author of the paper. “While it varies between different regions, there has been a global shift towards more frequent flash droughts during the past 64 years.”
The transition from slow droughts to flash droughts is more noticeable in East and North Asia, Europe, the Sahara, and the west coast of South America. In areas such as eastern North America, Southeast Asia, and North Australia, these droughts weren’t so common, but nevertheless, the speed of drought onset increased. The authors found no evidence of flash droughts in the Amazon and West Africa. In fact, in the Amazon, slow droughts have become more frequent in the past few years.
“As we head towards a warmer future, flash droughts are becoming the new normal. Our models show that higher-emission scenarios would lead to a greater risk of flash droughts with quicker onset, which pose a major challenge for climate adaptation,” said Professor Justin Sheffield.
The team believes these flash droughts may affect ecosystems more than slow droughts, as animals and plants don’t have enough time to adapt to a sudden lack of water and resources. In addition, forecasting these droughts is more difficult because current models use long time scales. We need new approaches to detect these flash droughts as early as possible, as well as a better understanding of how the environment will be impacted.
Yaun X et al. A global transition to flash droughts under climate change.Science380, 187-191(2023), https://www.science.org/doi/10.1126/science.abn6301