Warming Climate Driving Transition To More Frequent Flash Droughts

Anthropogenic climate change is driving an increase in the global frequency of “flash droughts,” according to a new study.

The findings reveal regions of the world particularly vulnerable to these droughts – rapid-onset drying events that appear with little warning – and underscore the urgency for adapting to them, as the land area over which they are expected to occur is projected to expand.

Droughts mainly originate from large-scale internal climate variability, occurring over interannual or seasonal time scales. However, recent studies have shown that droughts can also occur on sub-seasonal timescales and develop into severe droughts within weeks.

These rapid-onset flash droughts – which didn’t receive wide attention until the occurrence of the severe U.S. drought in the summer of 2012 – are difficult to predict and prepare for, making their impacts particularly severe. Although previous research has suggested that human-induced climate change has increased the frequency of flash droughts in some parts of the world, whether warming is driving a global transition toward flash drought as a “new normal” remains uncertain.

Using global reanalysis data on soil moisture, Xing Yuan and colleagues evaluated changes in the speed of drought onset worldwide over the past 64 years. The data show a transition toward more flash droughts over 74% of the global regions outlined by the IPCC Special Report on Extreme Events (SREX).

These drought events, say the authors, are associated with greater evapotranspiration and precipitation deficits attributable to anthropogenic climate change. According to Yuan et al., the transition toward increased flash droughts can be expected to expand to most land areas in the future, particularly under high-emission climate scenarios.

“With less time to prepare for flash droughts, proactive adaption is required rather than more costly reactive drought management,” write David Walker and Anne Van Loon in a related Perspective.

Early warning of flash drought onset on time scales of a few weeks can be hugely beneficial for mitigating their impacts and managing the risk of this new normal, say Yuan and colleagues.