Large ensemble simulations indicate increases in spatial compounding of droughts and hot extremes across multiple croplands in China

The simultaneous occurrence of extremes (e.g., droughts) at multiple regions (usually termed as spatial compounding of extremes), such as croplands, may lead to large impacts on global food security. Recently, the concurrent droughts and hot extremes at a specific location, which are referred to as compound droughts and hot extremes (CDHEs), have garnered considerable attention due to the potentially amplified impacts of individual extremes. Though the spatial compounding of individual droughts or hot extremes has been assessed, the variability of the spatial compounding of CDHEs across multiple croplands in China has been lacking due to relatively short records or small sample sizes. In this study, we evaluated changes in the spatial compounding of CDHEs across multiple croplands in China, including Songnen Plain (SN), North China Plain (NC), and Sichuan Basin (SC), based on precipitation and temperature data from CN05.1 and large ensemble model (CESM1-CAM5). Results show that the frequency of CDHEs in each region will increase in future periods especially for the eastern SN, central NC, and northern SC (increase by more than 15 months), with more than 70 % of the 40 ensemble members showing a large increase. Projected changes of different cases of spatial compounding of CDHEs in three croplands (i.e., SN-NC, NC-SC, SN-SC, SN-NC-SC) showed increases from 1961–2010 to 2031–2080. In particular, higher increases in the spatial compounding of CDHEs in the NC-SC region are projected (from 0.58 to 3.73 months on average), with the ratio of non-zero event members increasing from 47.5 % to 95 %. These results underscore the high risk of the spatial compounding of extremes at multiple croplands in China in the future.