Assessing the Response of Surface Cloud Radiative Effects to Stratospheric Aerosol Injections Over West and Central Africa

This study investigates the response of surface cloud radiative effects (CREs) to Assessing Responses and Impacts of Solar Climate Intervention on the Earth system with Stratospheric Aerosol Injection (ARISE-SAI) relative to Shared Socio-Economic Pathways (SSP2-4.5) across three regions: Southern West Africa (SWA), Central Africa (CA), and Sahara (SAH). We utilize 10 members of the simulations from the Community Earth System Model version 2 (CESM2) with the Whole Atmosphere Community Climate Model version 6 (WACCM6) under the ARISE-SAI-1.5 scenario, comparing the outputs to those from the SSP2.4-5 scenario. Compared to SSP2-4.5, the findings indicate that ARISE-SAI-1.5 has the potential to mitigate the decreasing trend of shortwave cloud cooling by −0.35, −0.99, and −0.20 W/m², while significantly enhancing the longwave warming by +1.06, +0.62, and +0.23 W/m², over CA, SWA, and SAH, respectively, during the period 2035–2069. However, the changes in shortwave cloud cooling are not robust and may be attributable to natural variability rather than the direct effects of ARISE-SAI. The changes in cloud radiative effects underpin high sensitivity to changes in liquid water path, while the increased fractional cloud cover contributes to enhancing longwave cloud warming at the surface. Results also reveal strengthened precipitation associated with increased shortwave cloud cooling effect outweighing its longwave counterpart on the one hand or increased shortwave cloud cooling and reduced longwave cloud warming on the other hand. It is noteworthy that our results, although based solely on ARISE-SAI-1.5 simulations, pave the way to comprehensive comparisons between model results for a better assessment of the impacts of SAI deployment.