The Human Health Impacts of Africas 21st Century Air Pollutant Emissions Trajectory

Using the Shared Socioeconomic Pathway scenarios (SSPs), transient future experiments were performed in UKESM1, investigating the effect of African emissions following a weak mitigation scenario (SSP3-RCP7.0) scenario whilst the rest of the world follows a strong mitigation scenario (SSP1-RCP1.9), relative to a global strong mitigation (SSP1-RCP1.9) control. SSP3 sees higher direct anthropogenic aerosol emissions, but lower biomass burning (BB) emissions, over Africa. Experiments were performed using SSP3-RCP7.0 for several sets of species: BB aerosol and reactive gas emissions (except CH4), nonBB aerosol and reactive gas emissions, both of these together, CO2 concentrations (with and without changing aerosol and reactive gases), and additionally changing CH4. The more polluted pathways resulted in significantly higher local and remote surface concentrations of PM2.5 and O3. Using concentration-response functions, we find that the differing pollutant levels drive substantial differences in the impacts on human health, with increases in air pollution mortality into the future under higher emissions scenarios, and with nonBB emissions playing a dominant role due to their co-location with large population centres.