Non-land-use forcing significantly drives projected trends of atmospheric black carbon over Africa: Implications for mitigation strategies.

Abstract

Black carbon (BC) plays a critical role in climate forcing and poses significant health risks, yet its trends and drivers remain poorly constrained across Africa. Here, we quantify the relative contributions of land-use and non-land-use forcing to the projected trends of BC using the Meteorological Research Institute Earth System Model version 2.0 (MRI-ESM2-0) under the Aerosol Chemistry Model Intercomparison Project (AerChemMIP). A variance decomposition framework is applied to SSP370SST and SSP370SST-SSP126Lu simulations to isolate land-use from non-land-use forcing. The MRI-ESM2-0 model reproduces spatial patterns well (r > 0.8, p < 0.05), although spatially heterogeneous biases persist over Central Africa. Elevated BC concentration (>0.7 μg m-3) occurs in Central and West Africa, while low (<0.1) concentrations occur in parts of North Africa and the island of Madagascar. Projected trends reveal a statistically significant increase in BC (p < 0.05) over North and West Africa, whereas Central and Southern Africa show decreasing trends in BC until 2100. The projected trends are primarily driven by non-land-use emissions, with the influence of hydroclimatic changes, while land-use forcing is most pronounced in Central and Southern Africa. These findings highlight the need for region-specific mitigation strategies to control future BC concentrations across Africa effectively.