Exploring uncertainty in dynamical future changes in Sahel precipitation: the extratropical influence

Abstract The future changes in Sahel precipitation have significant societal implications. Yet, the projections in Sahel precipitation remain highly uncertain, partly due to strong differences across climate models in projected sea surface temperature (SST) and its effects on the atmospheric circulation. This study investigates the effects of North Atlantic and Mediterranean SST changes on future Sahel precipitation through sensitivity experiments conducted with three atmospheric models. We confirm that the warming of the North Atlantic and the Mediterranean SSTs is one of the main reasons for the discrepancies between climate model projections of Sahel precipitation. Warming in the North Atlantic and Mediterranean enhances the monsoon circulation and increases precipitation over the Sahel, primarily through dynamical effects driven by energy gradients. At the same time, we identify non-linear responses to the Atlantic warming and substantial differences between the results of each model. Thus, reducing uncertainty in Sahel precipitation projections calls for improved understanding of two issues: first, Northern Hemisphere SST changes and their representation in climate models, and second, their effects on Sahel precipitation. Additionally, we find that uncertainty in future SST changes contributes to uncertainty in high-impact weather events.