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The Effects of Anthropogenic and Volcanic Aerosols and Greenhouse Gases on 20th Century Sahel Precipitation
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  • Rebecca Herman,
  • Michela Biasutti,
  • Alessandra Giannini,
  • Yochanan Kushnir
Rebecca Herman
Columbia University

Corresponding Author:rebecca.herman@columbia.edu

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Michela Biasutti
Lamont-Doherty Earth Observatory, Columbia University
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Alessandra Giannini
Laboratoire de Météorologie Dynamique,Earth Institute, Columbia University
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Yochanan Kushnir
Lamont-Doherty Earth Observatory of Columbia University
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There is little scientific consensus on the importance of external climate forcings—including anthropogenic aerosols, volcanic aerosols, and greenhouse gases (GHG)—relative to each other and to internal variability in dictating past and future Sahel rainfall. We address this query by relating a 3-tiered multi-model mean (MMM) over the Climate Model Intercomparison Project phase 5 (CMIP5) “20th century” and pre-Industrial control simulations to observations. The comparison of single-forcing and historical simulations highlights the importance of anthropogenic and volcanic aerosols over GHG in generating forced Sahel rainfall variability in models. However, the forced MMM only accounts for a small fraction of observed variance. A residual consistency test shows that simulated internal variability cannot explain the residual observed multidecadal variability, and points to model deficiency in simulating multidecadal variability in the forced response, internal variability, or both.