29 Sep 2022
29 Sep 2022
Status: this preprint is open for discussion.

Local and remote climate impacts of future African aerosol emissions

Christopher D. Wells1, Matthew Kasoar2, Nicolas Bellouin3, and Apostolos Voulgarakis2,4 Christopher D. Wells et al.
  • 1School of Earth and Environment, University of Leeds, Leeds, UK
  • 2School Leverhulme Centre for Wildfires, Environment and Society, Department of Physics, Imperial College London, London, UK
  • 3Department of Meteorology, University of Reading, Reading, UK
  • 4School of Environmental Engineering, Technical University of Crete, Chania, Greece

Abstract. The potential future trend in African aerosol emissions is uncertain, with a large range found in future scenarios used to drive climate projections. The future climate impact of these emissions is therefore uncertain. Using the Shared Socioeconomic Pathway (SSP) scenarios, transient future experiments were performed with the UK Earth System Model UKESM1, investigating the effect of African emissions following the high emission SSP370 scenario as the rest of the world follows the more sustainable SSP119, relative to a global SSP119 control. This isolates the effect of Africa following a relatively more polluted future emissions pathway. SSP370 sees higher direct anthropogenic aerosol emissions, but lower biomass burning emissions, over Africa. Increased aerosol reduces the local incident surface radiation, causing a local cooling, but the dominance of the black carbon absorption effect remotely from Africa leads to a global warming. The local cooling persists even when including the higher African CO2 emissions under SSP370 than SSP119. Precipitation also exhibits complex changes, with large-scale shifts in the Inter-Tropical Convergence Zone (ITCZ) due to hemispheric asymmetries in the applied forcing, and enhanced local rainfall due to mid-tropospheric instability from BC absorption. These results highlight the importance of future African aerosol emissions for regional and global climate, and the spatial complexity of this climate influence.

Christopher D. Wells et al.

Status: open (extended)

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on egusphere-2022-919', Anonymous Referee #1, 27 Oct 2022 reply

Christopher D. Wells et al.

Christopher D. Wells et al.


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Short summary
The climate is altered by greenhouse gases and air pollutant particles, and such emissions are likely to change drastically in the future over Africa. Air pollutants do not travel far, so their climate effect depends on where they are emitted. This study uses a climate model to find the climate impacts of future African pollutant emissions being either high or low. The particles absorb and scatter sunlight, causing the ground nearby to be cooler, but elsewhere the increased heat causes warming.