Model uncertainties in climate change impacts on Sahel precipitation in ensembles of CMIP5 and CMIP6 simulations
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Model uncertainties in climate change impacts on Sahel precipitation in ensembles of CMIP5 and CMIP6 simulations Paul‑Arthur Monerie1 · Caroline M. Wainwright1 · Moussa Sidibe2 · Akintomide Afolayan Akinsanola3 Received: 6 November 2019 / Accepted: 11 June 2020 © The Author(s) 2020
Abstract The impact of climate change on Sahel precipitation suffers from large uncertainties and is strongly model-dependent. In this study, we analyse sources of inter-model spread in Sahel precipitation change by decomposing precipitation into its dynamic and thermodynamic terms, using a large set of climate model simulations. Results highlight that model uncertainty is mostly related to the response of the atmospheric circulation to climate change (dynamic changes), while thermodynamic changes are less uncertain among climate models. Uncertainties arise mainly because the models simulate different shifts in atmospheric circulation over West Africa in a warmer climate. We linked the changes in atmospheric circulation to the changes in Sea Surface Temperature, emphasising that the Northern hemispheric temperature gradient is primary to explain uncertainties in Sahel precipitation change. Sources of Sahel precipitation uncertainties are shown to be the same in the new generation of climate models (CMIP6) as in the previous generation of models (CMIP5). Keywords Uncertainties · Climate models · West Africa · Projected changes · Atmospheric circulation
1 Introduction In Sahelian countries, around 65% of the labour force (FAO, 2006) and 95% of the land use (Rockström et al. 2004) are devoted to agriculture, which is predominantly rain-fed. About one-third of the gross domestic product depends on the agricultural sector, versus about 14% for developed nations. The monsoon season occurs between late June to late September (Liebmann et al. 2012; Dunning et al. 2016; Akinsanola and Zhou 2019a) and brings about 80% of the annual rainfall amount. As a result, the Sahelian countries are highly vulnerable to intraseasonal and multidecadal Electronic supplementary material The online version of this article (https://doi.org/10.1007/s00382-020-05332-0) contains supplementary material, which is available to authorized users. * Paul‑Arthur Monerie [email protected] 1
National Centre for Atmospheric Science, University of Reading, Reading, UK
2
Centre for Agroecology, Water and Resilience (CAWR), Coventry University, Coventry, UK
3
Department of Geography, University of Georgia, Athens, Georgia, USA
variability of the West African Monsoon. It has been shown that climate change could have robust impacts on agriculture yield (Sultan et al. 2014; Sultan and Gaetani 2016), river flow (Angelina et al. 2015; Aich et al. 2016; Stanzel et al. 2018; Sylla et al. 2018; Sidibe et al. 2020) and extreme precipitation events (Sylla et al. 2015; Han et al. 2019; Akinsanola and Zhou 2019a) over West Africa. However, projections for the end of the 21st century suffer from large uncertainties (Biasutti 2013; Monerie et al. 2016; Yan et al. 20
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