Fingerprints of external forcings on Sahel rainfall: aerosols, greenhouse gases, and model-observation discrepancies
Open Access
- 1 April 2020
- journal article
- research article
- Published by IOP Publishing in Environmental Research Letters
- Vol. 15 (8), 084023
- https://doi.org/10.1088/1748-9326/ab858e
Abstract
Over the 20th and 21st centuries, both anthropogenic greenhouse gas increases and changes in anthropogenic aerosols have affected rainfall in the Sahel. Using multiple characteristics of Sahel precipitation, we construct a multivariate fingerprint that allows us to distinguish between the model-predicted responses to greenhouse gases and anthropogenic aerosols. Models project the emergence of a detectable signal of aerosol forcing in the middle of the twentieth century and a detectable signal of greenhouse gas forcing at the beginning of the twenty-first. However, the signals of both aerosol and greenhouse gas forcing in observations emerge earlier and are stronger than in the models, far stronger in the case of aerosols. The similarity between the response to aerosol forcing and the leading mode of internal variability makes it difficult to attribute this model-observation discrepancy to errors in the forcing, errors in the forced response, model inability to capture the amplitude of internal variability, or some combination of these. For greenhouse gases, however, the forced response is distinct from internal variability as estimated by models, and the observations are largely commensurate with the model projections.This publication has 53 references indexed in Scilit:
- Identifying human influences on atmospheric temperatureProceedings of the National Academy of Sciences of the United States of America, 2012
- Global and regional evolution of short-lived radiatively-active gases and aerosols in the Representative Concentration PathwaysClimatic Change, 2011
- Regional‐scale convection patterns during strong and weak phases of the Saharan heat lowAtmospheric Science Letters, 2010
- Delayed Sahel rainfall and global seasonal cycle in a warmer climateGeophysical Research Letters, 2009
- The physical basis for increases in precipitation extremes in simulations of 21st-century climate changeProceedings of the National Academy of Sciences of the United States of America, 2009
- Recent trends in the Central and Western Sahel rainfall regime (1990–2007)Journal of Hydrology, 2009
- A global perspective on African climateClimatic Change, 2008
- Identification of human-induced changes in atmospheric moisture contentProceedings of the National Academy of Sciences of the United States of America, 2007
- Robust Sahel drying in response to late 20th century forcingsGeophysical Research Letters, 2006
- On the question of the “recovery” of the rains in the West African SahelJournal of Arid Environments, 2005