Asymmetric forcing from stratospheric aerosols impacts Sahelian rainfall

Sahelian drought is investigated by analysing de-trended observations between 1900 and 2010, which show that substantial Northern Hemisphere volcanic eruptions preceded three of the four driest summers. Modelling both episodic volcanic eruptions and geoengineering by continuous deliberate stratospheric injection shows that large asymmetric aerosol loadings in the Northern Hemisphere are a precursor of Sahelian drought, whereas if the aerosol loadings are concentrated in the Southern Hemisphere greening of the Sahel is induced.