Robust intensification of projected regional precipitation extremes over Africa.

Abstract

Extreme rainfall is increasing under climate warming, but its future patterns across Africa remain highly uncertain. Using Coupled Model Intercomparison Project Phase 6 (CMIP6) simulations, we assess projected changes in annual maximum one-day precipitation (Rx1day) and rare precipitation extremes across African subregions under both SSP2-4.5 and SSP5-8.5 scenarios. Our results show robust intensification of Rx1day by the late twenty-first century, with increases of ~5-10 mm day⁻¹ (15-23 mm day⁻¹) under SSP2-4.5 (SSP5-8.5), largest in convectively dominated equatorial regions such as West, Central, and Northeast Africa. Rare events that historically occurred once every 50 (100) years are projected to recur every ~5-10 ( ~ 6-14) years, with recurrence intervals as short as 2-3 years in equatorial regions under SSP5-8.5. This intensification is driven primarily by thermodynamic moistening associated with radiation-induced warming, while diabatic heating-driven dynamic changes modulate regional responses and account for much of the intermodel spread. A hierarchical emergent-constraint framework based on observed historical global mean surface temperature trends moderates mean Rx1day intensification by ~11-35% without altering its sign. Constrained and unconstrained projections indicate substantial continent-wide increases in population and gross domestic product exposure.