Wane Dahirou, Giannini Alessandra, Kaplan Alexey, Gaye Amadou T
International Research Laboratory Environnement, Santé, Sociétés (IRL3189) Centre National de la Recherche Scientifique (CNRS), France and Université Cheikh Anta Diop, Dakar, Senegal.
Laboratoire de Physique de l'Atmosphère et de l'Océan-Siméon Fongang Ecole Supérieure Polytechnique de l'Université Cheikh Anta Diop, Dakar, Senegal.
Sci Adv. 2025 Aug 22;11(34):eadu5415. doi: 10.1126/sciadv.adu5415. Epub 2025 Aug 20.
In the 1970s and 1980s, the semi-arid Sahel, the southern edge of the Sahara Desert, experienced spatially uniform drought, from the Atlantic Ocean to the Red Sea. The recovery that ensued is projected to continue in the center and east, leaving the west out. We show that these two patterns-uniform variation and east-west contrast-are present in instrumental observations and in simulations with constant or time-varying external forcing. Uniform variation is amplified by 20th century external forcing, while a global warming-induced strengthening of the monsoon seeds the east-west contrast. This contrast is deepened by a mid-21st century transition to a North Atlantic cooling relative to the global tropical oceans, which affects the western Sahel most strongly because it is immediately adjacent to the North Atlantic, leading to a divergence in outcomes-between a progressively wetter central and eastern Sahel and an abruptly drier western Sahel-that is unparalleled in instrumental observations.
在20世纪70年代和80年代，半干旱的萨赫勒地区（撒哈拉沙漠南缘）经历了从大西洋到红海的空间均匀干旱。随后的恢复预计将在中部和东部继续，而西部则除外。我们表明，这两种模式——均匀变化和东西部对比——存在于仪器观测以及恒定或随时间变化的外部强迫模拟中。20世纪的外部强迫放大了均匀变化，而全球变暖导致的季风增强则引发了东西部对比。到21世纪中叶，相对于全球热带海洋，北大西洋出现降温，这种对比进一步加深，这对萨赫勒西部地区影响最为强烈，因为它紧邻北大西洋，导致了观测记录中前所未有的结果差异——萨赫勒中部和东部逐渐变湿，而西部则突然变干。
