Amplified future risk of compound droughts and hot events from a hydrological perspective

Abstract

Global warming can result in changes in droughts and hot events (or compound droughts and hot events, CDHEs), which can take a heavy toll on the society and environment. Recent studies have made substantial progress in the projection of these events. However, previous projection studies mostly focus on the concurrences of meteorological droughts and hot events but ignore the difference among various CDHEs. Specifically, the concurrence of hot events and different types of droughts (e.g., agricultural droughts and hydrological droughts) has been seldom explored from a hydrological perspective. Based on phase six of the Coupled Model Intercomparison Project (CMIP6), we evaluate changes in different types of CDHEs, including compound meteorological drought-hot events (CMDHEs), compound agricultural drought-hot events (CADHEs) and compound hydrological drought-hot events (CHDHEs), for different future periods at the global scale. Based on comparisons with data from Global Land Data Assimilation System Version 2 (GLDAS-2.0), CMIP6 can reproduce the overall spatial distribution and temporal variation of different CDHEs at the global scale. In addition, the frequency and spatial extent of the three compound events show a marked increase during different future periods relative to the base period 1995–2014. The projected increase in global average frequency of CMDHEs in the long term period is lower than that of CADHEs (increase by 73.74% and 113.95% for CMDHEs and CADHEs, respectively). The uncertainty in the simulation of CADHEs and CHDHEs is relatively larger than CMDHEs in the future periods over most regions. The results of this study highlight the urgent demand for adaptation measures of CDHEs to cope with compound extremes in the future.