title: Local biomass burning is a dominant cause of the observed precipitation reduction in southern Africa.
abstract: Observations indicate a precipitation decline over large parts of southern Africa since the 1950s. Concurrently, atmospheric concentrations of greenhouse gases and aerosols have increased due to anthropogenic activities. Here we show that local black carbon and organic carbon aerosol emissions from biomass burning activities are a main cause of the observed decline in southern African dry season precipitation over the last century. Near the main biomass burning regions, global and regional modelling indicates precipitation decreases of 20-30%, with large spatial variability. Increasing global CO2 concentrations further contribute to precipitation reductions, somewhat less in magnitude but covering a larger area. Whereas precipitation changes from increased CO2 are driven by large-scale circulation changes, the increase in biomass burning aerosols causes local drying of the atmosphere. This study illustrates that reducing local biomass burning aerosol emissions may be a useful way to mitigate reduced rainfall in the region.
authors.affiliation: Center for International Climate and Environmental Research-Oslo (CICERO), P.O. Box 1129 Blindern, N-0318 Oslo, Norway.
authors.forename: Øivind
authors.initials: Ø
authors.lastname: Hodnebrog
authors.affiliation: Center for International Climate and Environmental Research-Oslo (CICERO), P.O. Box 1129 Blindern, N-0318 Oslo, Norway.
authors.forename: Gunnar
authors.identifier: http://orcid.org/0000-0002-4309-476X
authors.initials: G
authors.lastname: Myhre
authors.affiliation: School of Earth and Environment, University of Leeds, Leeds LS2 9JT, UK.
authors.forename: Piers M
authors.initials: PM
authors.lastname: Forster
authors.affiliation: Center for International Climate and Environmental Research-Oslo (CICERO), P.O. Box 1129 Blindern, N-0318 Oslo, Norway.
authors.forename: Jana
authors.initials: J
authors.lastname: Sillmann
authors.affiliation: Center for International Climate and Environmental Research-Oslo (CICERO), P.O. Box 1129 Blindern, N-0318 Oslo, Norway.
authors.forename: Bjørn H
authors.initials: BH
authors.lastname: Samset
mesh_terms: D000353:Africa, Southern; D001272:Atmosphere; D018533:Biomass; D005390:Fires; D008962:Models, Theoretical; D011891:Rain