Asymmetric forcing from stratospheric aerosols impacts Sahelian rainfall

Asymmetric forcing from stratospheric aerosols impacts Sahelian rainfall IAGP Investigator Jim Haywood based at the Met Office publishes his latest research in Nature Climate Change Using state of the art climate models this latest study shows how the Sahelian droughts of the 1970s-1990s may have been caused, to a much greater degree than previously understood, by significant volcanic eruptions in the Northern Hemisphere.  The Sahel is a belt of land that crosses the African continent along the southern border of the Sahara Desert and is described as one of the poorest and most vulnerable regions of the world. Here rainfall is generally low and unpredictable. The detection of this link between volcanic activity and drought could be used by policy-makers and aid organisations to potentially predict, and so limit, the devastating humanitarian impact of prolonged drought in this region. The study also demonstrates how the use of stratospheric aerosols, a geoengineering technology designed to cool the earth by reflecting more sunlight back out into space, has an impact on precipitation similar to that of volcanic eruptions.  By using climate models the research showed that injecting sulphur dioxide particles into the stratosphere over the Northern Hemisphere could lead to more sunlight being reflected back into space and so reducing the levels of precipitation in the Southern Hemisphere, whilst injections carried out in the Southern Hemisphere could lead to increased rainfall in the Sahel. However it would not be possible to limit the effect to this region, with attempts to increase rainfall in the Sahel possibly leading to decreased precipitation in other parts of the Southern Hemisphere. This creation of potential winners and losers highlights the complexity and emotive nature of geoengineering.  DOI: 10.1038/NCLIMATE1857 Read more about this study on the Met Office website Listen to Jim Haywood discuss his research on YouTube