The fast response of Sahel precipitation to climate change allows effective mitigation action

Paul-Arthur Monerie,Marco Gaetani,Benjamin Pohl

doi:10.1038/s41612-021-00179-6

Abstract

Climate change will drive major perturbations of the West African summer monsoon. A zonal contrast in precipitation will develop at the end of the century, with an increase in precipitation over the central Sahel and a decrease in precipitation over the western Sahel. Such a zonal contrast results from the antagonist effects of the fast (due to enhanced radiative warming over land, and over the North Hemisphere, relative to the South Hemisphere) and slow (associated with long-term changes in oceanic circulation) responses of precipitation to increasing greenhouse gases. While such changes have already been assessed, less attention has been given to their temporality, an issue of major importance to promote efficient mitigation and adaptation measures. Here, we analyse the future evolution of precipitation changes decomposed into a fast and a slow response, showing that the fast response dominates the slow one. From this evidence, we highlight that mitigation strategies may be successful at reducing the effect of climate change on Sahel precipitation within a few decades, by muting the fast response. This decomposition also allows for a better understanding of the uncertainty of climate model predictions in Africa.

Highlights

Climate simulations performed in the framework of the Coupled Model Intercomparison projects (CMIP3-51–3) show that the effects of anthropogenic activity on Sahel precipitation are highly uncertain
Show two poles emerging at the end of the 21st century[6,33,35], we show that precipitation changes in western and central Sahel are linked to different mechanisms, that changes on different time scales
Central Sahel precipitation change is associated with the fast response to climate change, and occurs at a higher rate than that for western Sahel precipitation, which is associated with the slow response to climate change, at the end of the 21st century

Summary

Introduction

Climate simulations performed in the framework of the Coupled Model Intercomparison projects (CMIP3-51–3) show that the effects of anthropogenic activity on Sahel precipitation are highly uncertain. Models project either increases or decreases in Sahel precipitation by the end of the 21st century[4], with the inter-model spread in precipitation change exceeding the multi-model mean change[5,6] Such uncertainty primarily originates from differences among climate models to simulate the response of the atmospheric circulation to changes in greenhouse gas (GHG) concentrations[6,7]. The zonal contrast in precipitation changes strengthens with warming[11], is reproduced by a majority of climate models and found in numerous emission scenarios[4,9,10,19,20,21] This precipitation change pattern has strong effects on local communities, as it is associated with heterogeneous impacts on agriculture[22], occurrence of precipitation extreme events[23], modification of monsoon onset and withdrawal dates[17]

Methods

Results

Conclusion