The Occurrence of "Flash Droughts" is on the Rise

A new study finds that fast-forming droughts are becoming more common and occurring with greater speed in many parts of the world due to climate change. Known as “flash droughts,” these types of droughts are replacing slower onset droughts and are harder to predict and prepare for, which could make their management more difficult. Most major droughts have tended to occur over seasonal or yearly time scales, resulting from variability in large-scale climate patterns such as El Niño. But in roughly the last six decades, there has been a transition towards more droughts that form over just a few weeks with little warning in most parts of the world.

This finding has implications for ecosystem conservation and agricultural management. Will some species of plants be less able to survive a trend towards flash droughts? What would that mean for biodiversity or the amount of carbon stored in an ecosystem? Flash droughts can cause significant damage to agriculture and contribute to other extreme weather events such as wildfires and heat waves. In the summer of 2012, a severe flash drought across the United States caused over $30 billion in damages, and no climate models predicted it.

To address the issue and prepare for the future, Xing Yuan, a hydrologist at Nanjing University of Information Science and Technology in China, and colleagues analysed soil moisture data from around the world from 1951 to 2014. Through their research, they found that the speed of drought onset on sub-seasonal scales has increased in much of the world, and the ratio of fast to slow droughts has increased in over 74 percent of global regions set out by the Intergovernmental Panel on Climate Change Special Report on Extreme Events.

The climate anomalies driving these flash droughts, such as heat waves, are more extreme than those that drive seasonal or interannual droughts, leading to severe droughts in a shorter time. As the world continues to warm, causing more evapotranspiration and less rainfall, flash drought frequency is expected to continue to rise. Predicting flash droughts is challenging as current monitoring systems often cannot capture their onset at short enough time scales, so researchers advocate for exploring the mechanisms behind flash droughts and improving simulations, perhaps with the help of artificial intelligence.