Multi‐Model Impacts of Dust on African Air Quality and Mortality Under Regional and Global Anthropogenic Aerosol Changes

Decreases in anthropogenic aerosols will reduce fine particulate matter (PM_2.5); however, meteorological feedbacks alter dust emissions, modifying air quality gains. We use eight Earth System Models from the Regional Aerosol Model Intercomparison Project (RAMIP) simulations to assess African climate and air quality responses to anthropogenic aerosol emission perturbations, including meteorological feedbacks on dust emissions. By 2050, African and global emissions reductions drive the largest continent-average PM_2.5 decrease (0.92 ± 0.17 μg m⁻³; 5% and 1.35 ± 0.50 μg m⁻³; 7%, respectively) relative to SSP3-7.0, though regional dust increases partially offset these reductions. Anthropogenic emissions reductions in the U.S. and Europe also lower African PM_2.5 by 0.29 ± 0.32 μg m⁻³ (2%) due to teleconnections of Northern Hemisphere warming influencing the Intertropical Convergence Zone. Inter-model variability in dust and total PM_2.5 reflects differences in meteorological responses and dust emission parameterizations. Meteorological responses explain 90% of dust emissions variability across regions. Aerosol-driven climate feedbacks on dust account for up to 70% of total PM_2.5 changes in the Sahara and Namib, offsetting up to 20% of anthropogenic PM_2.5 reductions across Africa. Under 2050 global and Africa-wide anthropogenic aerosol reductions, 96,000 (95% CI: 54,000–137,000) and 84,000 (95% CI: 43,000–125,000) PM_2.5-related deaths are avoided in Africa, respectively. Dust PM_2.5 contributes an uncertain 3.4% of the avoided deaths under global reductions and has no net effect under Africa-wide reductions. Aerosol-driven climate feedbacks may partially offset direct air quality gains, though their continental-scale contribution remains small and uncertain.

Plain Language Summary
Future reductions in human-caused aerosol emissions are expected to lower the concentrations of PM_2.5 (fine particles smaller than 2.5 μm), but climate responses from the reductions can also alter natural dust emissions, which may offset or enhance these improvements. Using climate model simulations, we examined how reductions in regional and global human-caused emissions affect African air quality, including the role of climate-driven changes in dust. By 2050, reductions in African and global human-caused emissions lead to the largest decreases in PM_2.5 across the continent. Human-caused emission reductions in the United States and Europe also reduce PM_2.5 in Africa by modifying large-scale atmospheric circulation and long-range transport of pollution. In the Sahara and Namib deserts, changes in dust accounts for up to 70% of total PM_2.5 changes, while in West and East Africa, climate-driven increases in dust can offset up to 20% of air quality improvements. Overall, global and Africa-wide human-caused emission reductions could prevent about 96,000 and 84,000 PM_2.5-related deaths by 2050, though dust feedbacks may modify the magnitude of these health benefits.