20 April 2023

Flash droughts are becoming the new normal


In six decades, flash droughts have increased in 74 percent of the Planet’s regions, says a Chinese study. Climate change remains the main critical factor

by Matteo Cavallito


Flash drought, the phenomenon of sudden water shortage, is reportedly becoming more frequent on a global scale due to climate change, says a study by a group of Chinese researchers led by National Natural Science Foundation of China professor Xing Yuan and published in the journal Science. These phenomena, the researchers point out, are progressively replacing their long-term counterparts, implicitly posing special prediction and management difficulties.

The investigation looked at soil moisture data worldwide from 1951 to 2014 and calculated the rate of soil drying at the beginning and end of critical periods. According to the researchers, human-induced global warming remains the main cause of this trend, which is characterized by the onset of more extreme heat waves in comparison with those occurring during seasonal droughts.

74 percent of the planet’s regions are affected

“Flash droughts have occurred frequently worldwide, with a rapid onset that challenges drought monitoring and forecasting capabilities,” the research says. “Drought intensification rates have sped up over subseasonal time scales and that there has been a transition toward more flash droughts over 74% of the global regions identified by the Intergovernmental Panel on Climate Change Special Report on Extreme Events during the past 64 years.”

In the future, moreover, “is associated with amplified anomalies of evapotranspiration and precipitation deficit caused by anthropogenic climate change.” These findings “underscore the urgency of adapting to more rapid droughts in a future characterized by high temperatures.” The phenomenon is most notable in East and North Asia, Europe, Australia, the Sahara and the west coast of South America.

Toward a long-term drought

Flash droughts are a very recent concept, the researchers point out. The phenomenon had been described as early as the beginning of this century, but scientists’ attention would come to it with some delay. Striking the attention of observers was the severe U.S. drought of summer 2012, considered one of the worst since the 1930s and capable of producing economic losses of more than $30 billion.

“One of the distinctive features of this drought was its extremely rapid onset, with many locations going from drought-free to extreme drought conditions within a month,” the study recalls.

This water shortage was not predicted by any prior analysis model. In this regard, the authors again note, it is worth noting how some sudden droughts can be viewed as the initial phase of a long-term phenomenon, “the impacts of which are amplified by a subsequent persistent period of severe drought condition.” Even when they do not evolve into seasonal droughts, these events still have substantial impacts on vegetation growth and can trigger extreme phenomena such as heat waves or wildfires.

Climate change is the main factor

The study’s conclusions come alongside the findings of a recent report released by the Global Water Monitor Consortium, an initiative of the Australian National University, which found that global warming is altering the water cycle with obvious consequences for the environment and humans. Chinese researchers predict that flash droughts will further increase causing water to evaporate from soil and plants into the atmosphere.

“The increasing drought onset speed primarily comes from intensifying rainfall deficit and increasing evapotranspiration caused by anthropogenic climate change, which quickly dries the soil and creates ideal conditions for heat waves,” the research points out.

The transition to sudden water shortage events, moreover, can have irreversible impacts on the Earth’s environment. Indeed, because of the very rapid nature of these phenomena, “ecosystems may not have enough time to adapt to the sudden onset of large water deficits and heat extremes, resulting in a rapid reduction in ecosystem productivity,” the study concludes.