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Changes in climate extremes over West and Central Africa at 1.5?°C and 2?°C global warming

Diedhiou A., Bichet A., Wartenburger R., Seneviratne S.I., Rowell D.P., Sylla M.B., Diallo I., Todzo S., Touré N.E., Camara M., Ngounou Ngatcha B., Kane N.A., Tall L., Affholder F.. 2018. Environmental Research Letters, 13 (6) : 12 p..

In this study, we investigate changes in temperature and precipitation extremes over West and Central Africa (hereafter, WAF domain) as a function of global mean temperature with a focus on the implications of global warming of 1.5?°C and 2?°C according the Paris Agreement. We applied a scaling approach to capture changes in climate extremes with increase in global mean temperature in several subregions within the WAF domain: Western Sahel, Central Sahel, Eastern Sahel, Guinea Coast and Central Africa including Congo Basin. While there are several uncertainties and large ensemble spread in the projections of temperature and precipitation indices, most models show high-impact changes in climate extremes at subregional scale. At these smaller scales, temperature increases within the WAF domain are projected to be higher than the global mean temperature increase (at 1.5?°C and at 2?°C) and heat waves are expected to be more frequent and of longer duration. The most intense warming is observed over the drier regions of the Sahel, in the central Sahel and particularly in the eastern Sahel, where the precipitation and the soil moisture anomalies have the highest probability of projected increase at a global warming of 1.5?°C. Over the wetter regions of the Guinea Coast and Central Africa, models project a weak change in total precipitation and a decrease of the length of wet spells, while these two regions have the highest increase of heavy rainfall in the WAF domain at a global warming of 1.5?°C. Western Sahel is projected by 80% of the models to experience the strongest drying with a significant increase in the length of dry spells and a decrease in the standardized precipitation evapotranspiration index. This study suggests that the 'dry gets drier, wet gets wetter' paradigm is not valid within the WAF domain.

Mots-clés : précipitation; température; réchauffement global; changement climatique; afrique centrale; afrique occidentale; guinée; sahel

Thématique : Météorologie et climatologie

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