Meteorological to Agricultural Drought Transitions Compounded by Heat Waves in Historical and Future Climates

Abstract Meteorological droughts (persistent precipitation deficits) often, but not always, transition into agricultural droughts (persistent soil moisture deficits). The intensity of agricultural drought, however, can vary for a given precipitation deficit due to a number of catalyzing co‐factors beyond precipitation such as atmospheric evaporative demand and temperature. In this study we use Earth System Model data to quantify (a) how warm temperature anomalies affect this evolution from meteorological‐to‐agricultural drought and (b) how the evolution of droughts from historical and future climate scenarios differ. We benchmark these results against observational data and use a multi‐model ensemble to quantify agreement on future drought propagation. Broadly speaking, drought temperatures in the upper third of local distributions correspond with shifts on the order of 5 percentile of the soil moisture distribution. We would expect today's meteorological droughts to propagate into agricultural droughts roughly one drought classification more severe in the SSP3‐7.0 scenario in most regions. Even regions with increases in precipitation are likely to see more intense meteorological‐to‐agricultural drought propagation by the end of the 21st century. Models disagree on drought propagation changes in Africa for the same precipitation deficit, but suggest that all historical droughts would have had worse agricultural droughts in Europe and Eastern North America if they happened under SSP3‐7.0. When accounting for precipitation changes—which tend toward more frequent accumulated precipitation deficits—the increased severity of meteorological‐to‐agricultural drought evolution leads to predictions of major increases in moderate to extreme (D1–D3) drought events in all regions globally by the end of the century.