Stratospheric aerosol geoengineering (SAG) is suggested as a potential way to reduce the climate impacts of global warming. Using simulations from the Geoengineering Large Ensemble project that employed stratospheric sulfate aerosols injection to keep global mean surface temperature and also the interhemispheric and equator‐to‐pole temperature gradients at their 2020 values (present‐day climate) under Representative Concentration Pathway 8.5 scenario, we investigate the potential impact of SAG on the West African Summer Monsoon (WASM) precipitation and the involved physical processes. Results indicate that under Representative Concentration Pathway 8.5, during the monsoon period, precipitation increases by 44.76%, 19.74%, and 5.14% compared to the present‐day climate in the Northern Sahel, Southern Sahel, and Western Africa region, respectively. Under SAG, relative to the present‐day climate, the WASM rainfall is practically unchanged in the Northern Sahel region but in Southern Sahel and Western Africa regions, rainfall is reduced by 4.06% (0.19 ± 0.22 mm) and 10.87% (0.72 ± 0.27 mm), respectively. This suggests that SAG deployed to offset all warming would be effective at offsetting the effects of climate change on rainfall in the Sahel regions but that it would be overeffective in Western Africa, turning a modest positive trend into a negative trend twice as large. By applying the decomposition method, we quantified the relative contribution of different physical mechanisms responsible for precipitation changes under SAG. Results reveal that changes in the WASM precipitation are mainly driven by the reduction of the low‐level land‐sea thermal contrast that leads to weakened monsoon circulation and a northward shift of the monsoon precipitation.

中文翻译：

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平流层气溶胶地球工程作用下西非夏季风季风的变化

建议平流层气溶胶地球工程（SAG）作为减少全球变暖对气候的影响的一种潜在方法。使用来自地球工程大集合项目的模拟，该模拟采用平流层硫酸盐气溶胶注入，在代表浓度路径8.5情景下，将全球平均表面温度以及半球和赤道至极点的温度梯度保持在2020年的值（当今气候），我们研究SAG对西非夏季风（WASM）降水及其相关物理过程的潜在影响。结果表明，在代表浓度路径8.5下，季风期​​间，与北萨赫勒地区，南萨赫勒地区和西非地区的当前气候相比，降水分别增加了44.76％，19.74％和5.14％。在SAG模式下，相对于今天的气候，萨赫勒北部地区的WASM降雨量几乎没有变化，但萨赫勒南部和西非地区的WASM降雨量分别减少了4.06％（0.19±0.22 mm）和10.87％（0.72±0.27）毫米）。这表明，为抵消所有变暖而部署的SAG可以有效抵消气候变化对萨赫勒地区降雨的影响，但在西非则可能过度有效，将适度的积极趋势变成消极趋势的两倍。通过应用分解方法，我们量化了SAG下造成降水变化的不同物理机制的相对贡献。