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.

气候变化将推动西非夏季风的重大扰动。到本世纪末，降水将形成区域对比，萨赫勒中部地区的降水量将增加，而萨赫勒西部地区的降水量将减少。这种区域差异是由于降水对水的响应迅速（由于相对于南半球的陆地和北半球辐射增暖增强）和缓慢（与海洋环流的长期变化有关）的拮抗作用而产生的。增加温室气体。尽管已经评估了此类变化，但对它们的时效性的关注却很少，这是促进有效缓解和适应措施的重要问题。这里，我们分析了降水变化的未来演变，将其分解为快速响应和缓慢响应，这表明快速响应在慢响应中占主导地位。从这一证据中，我们强调指出，通过降低快速响应，缓解策略可能会在几十年内成功减少气候变化对萨赫勒地区降水的影响。这种分解还可以更好地了解非洲气候模型预测的不确定性。