Evolution of the probability of record-shattering spatially compounding droughts in a changing climate

Record-shattering events, defined as extreme events that exceed previous records by large margins, pose increasing risks under climate change. Concurrent soil moisture droughts across multiple crop-growing regions can severely impact the agricultural sector and global food security by exposing a large fraction of the global crop area to water stress. Here, using soil moisture data from Single Model Initial-condition Large Ensembles (SMILEs) over 1950-2099, we investigate the evolution of the probability of spatially compound droughts that shatter previous records in terms of total global crop area affected by droughts within the same year. Our results indicate that trends in mean soil moisture related to climate change are the major driver in the evolution of the record-shattering compound drought probability, while changes in variability (standard deviation of the time series)  are less important. We further attribute changes in the probability of such global-scale record-shattering events to trends in soil moisture in individual large crop-growing regions. By separating the distinct roles of long-term trends in mean conditions, variability of the soil moisture time series, as well as contributions from individual regions to global-scale record-shattering droughts across breadbaskets, this study provides novel insights on compound events threatening the global food security system.