Africa’s climate response to stratospheric aerosol injection materials

This study assessed Africa’s climate response to different injection materials for stratospheric aerosol geoengineering (SAG) using simulations from the SOCOLv4 model, which provides a set of SAG simulations following the G6sulfur experiment in the Geoengineering Multi-model Intercomparison Project (GeoMIP). We analysed four SAG experiments, which used four injection materials (sulfur, alumina, calcite, and diamond) referred to as G6sulfur, G6alumina, G6calcite, and G6diamond, respectively. The SAG experiments used a high-emission pathway (SSP5-8.5) as baseline in which each material was injected into the equatorial stratosphere to keep global warming levels similar to an intermediate emission pathway (SSP2-4.5). We assessed Africa’s climate response to these SAG materials by quantifying the end-of-century (2080-2099) mean changes in minimum and maximum temperatures and precipitation relative to SSP2-4.5. Our findings suggest that all injection materials show a cooling potential by keeping annual and seasonal minimum and maximum temperatures below SSP2-4.5 across most parts of the continent. Maximum and minimum temperatures could decrease the most between 10°S and 10°N, along the Guinean coast of west Africa and parts of Central Africa, by up to -2°C and -4°C, respectively. This SAG-induced cooling remains partial over north Africa where a residual warming of about 1°C could persist at the end of the century relative to the SSP2-4.5, irrespective of the injection material. On the other hand, the impact on precipitation is less linear and spatially heterogeneous. However, SAG could reverse the SSP5-8.5 projected mean continental and regional (especially over Central Africa) increases in annual and seasonal precipitation, inducing a dryer future under SAG across the continent, irrespective of the injection material. Our results further suggest that, relative to SSP2-4.5, G6alumina could cause the largest precipitation decrease and G6diamond the slightest decrease at the end of the century. In summary, our results show that irrespective of the injection material, SAG could significantly decrease temperatures across Africa, however lower warming and drying could still be achieved under SSP2-4.5, over parts of Africa.