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).
Highlights
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
Within the CMIP5 ensemble, stronger correlations are found between ΔP and ΔP, with r = 0.71 when considering western Sahel precipitation and r = 0.84 when considering central Sahel precipitation, showing that, in addition to the uncertainty in simulating changes in temperature over the ocean, uncertainties in simulating sea surface temperature (SST)—Sahel precipitation teleconnections have to be assessed
We analysed the causes of the uncertainties in simulating future changes in precipitation over the Sahel, using a set of 29 CMIP5 simulations and of 11 Climate Model Intercomparison Project Phase-6 (CMIP6) simulations
Summary
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. 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. Projections for the end of the 21st century suffer from large uncertainties (Biasutti 2013; Monerie et al 2016; Yan et al 2018), with some models simulating an increase in precipitation while others simulates a decrease in precipitation alongside strong differences in precipitation change patterns over West Africa
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