Dynamic and thermodynamic drivers of regional drought changes in Africa under different global warming levels

Abstract Drought events pose severe threats to socio-economic stability, with impacts particularly pronounced across Africa due to limited adaptive capacity. This study provides a comprehensive assessment of projected changes in drought characteristics, their physical drivers, and socioeconomic implications under different global warming levels (GWLs) and emission scenarios. In this study, we use 31 Coupled Model Intercomparison Project Phase 6 (CMIP6) models and identify drought events using the Standardized Precipitation Evapotranspiration Index (SPEI). We find a robust increase in drought frequency and duration across the Mediterranean (MED), Southern Africa (SAF), and Madagascar (MDG) across all GWLs and scenarios, while Central Africa (CAF) shows a decrease. Although drought intensity generally increases, these changes are mostly not robust because of high inter-model disagreement. Model uncertainty is identified as the dominant source of projection uncertainty, accounting for over 60% of the total variance. Furthermore, we assess the Time of Emergence (ToE) when the signal of drought metrics becomes distinct from natural variability and find that, the ToE of changes in drought frequency and intensity occurs earlier than that of drought duration. Moisture-budget analysis reveals distinct regional mechanisms underlying these changes, with drought intensification linked primarily to weakened vertical thermodynamic contributions over MED, reduced evaporation over SAF, and a combination of reduced evaporation and vertical dynamic contributions over MDG. These projected changes translate into substantial socioeconomic risks, with more than 200 million people and USD 30 billion in GDP projected to be exposed to drought across MED, SAF, and MDG at 3 °C GWL, while limiting warming to 1.5 °C could avoid approximately 70% of these impacts.