Flash drought is a new phenomenon with increasing prominence under global warming. The drought develops rapidly without sufficient early warning, and has stricken the world with severe impacts during recent years. This raises an urgent need to investigate flash drought risk and its underlying drivers in a changing climate.

"How the flash drought risk will change in a warming future climate remains unknown for a number of reasons," said YUAN Xing from the Nanjing University of Information Science & Technology, "For example, there’s a diversity of flash drought definition that scientists haven’t agreed upon, the role of anthropogenic fingerprints is not clear, and we are not sure of future socioeconomic scenarios."

YUAN and his PhD students WANG Linying, JI Peng, and ZHANG Miao from the Institute of Atmospheric Physics (IAP) of the Chinese Academy of Sciences, Dr. Peili WU from the UK Met Office and Prof. Justin SHEFFIELD from the University of Southampton, addressed the above issues in a recently published study in Nature Communications.

Their study focused in China, and they proposed a new definition of flash drought based on rapid decline rate of soil moisture and the dry persistency. The new definition captures both the "flash" and "drought" characteristics, and the duration constraint gives enough time for a flash drought event to cause ecological impacts.

"We carried out land surface ensemble simulations driven by multiple climate models under different external forcings, such as greenhouse gases," said YUAN.

Results showed a significant increasing trend of flash drought frequency over China during 1961-2005, with clear 77% footprint from anthropogenic greenhouse gas emissions. Under moderate emission scenarios, the exposure risk in China will increase by 23%±11% in the middle of this century. This increase can reach up to 40% in the southern provinces with humid climate (such as Guizhou, Guangxi, Guangdong, Zhejiang, etc.), while the exposure risk in semi-arid northern areas will decrease.

"This indicates that anthropogenic climate change has changed the traditional arid areas, and more attention should be paid to deal with the flash drought risks in humid and semi-humid areas," said YUAN.