Variability and changes in heatwave characteristics over West Africa

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Abstract Using observed climate data from Princeton datasets (1981-2010) and CMIP6 climate projections for 2041-2100 under various climate change scenarios (SSP1-2.6, SSP2-4.5, SSP3-7.0, SSP5-8.5), we have highlighted heatwave characteristics over West Africa under climate change. Our findings highlight that the downscaled CMIP6-averaged multi-model exhibits strong structural similarity (major spatial similarities) that largely outweigh the few minor quantitative differences observed. A pronounced increase in heatwave frequency, with periods exceeding 40 days, has been observed in the northern, southern, and eastern extensions of Mali. The SSP3-7.0 and SSP5-8.5 scenarios project protracted heatwaves lasting over 90 days across most of the northern region, except along the Atlantic coast and in parts of the south. Heatwave duration is expected to range from 50 to 140 days, with notable amplification under the SSP3-7.0 and SSP5-8.5 scenarios, particularly along the Senegal-Mauritania coastline. The amplitude of these heatwaves is estimated at 24°C² (°C x °C) in the SSP5-8.5 scenario, compared with 2 to 6°C² in the southern region. The analysis reveals significant regional variability, with heatwaves intensifying in the mountainous regions of the Gulf of Guinea, southern Nigeria, and the central Sahel, as the model also simulates. Principal component analysis indicates an increased frequency of heatwaves, characterized by longer durations and greater amplitudes, particularly under intense warming scenarios. These projections underscore the need for targeted adaptation, particularly in the most vulnerable regions, such as northern Mauritania, Mali, and Niger, to mitigate the impacts of anticipated climate change.