Projected change in occurrence and severity of heatwaves over West Africa as simulated by CMIP6 models

Abstract This study examines both recent and future changes in the occurrence and severity of heatwaves over West Africa using ensemble means from five CMIP6 models. The analysis covers three time periods: 2016–2040 (present era), 2041–2065 (near future), and 2066–2090 (far future), under three Shared Socio-economic Pathway (SSP) emission scenarios: SSP1-2.6, SSP2-4.5, and SSP5-8.5. Ensemble means of the daily minimum and maximum temperatures were used, alongside the 95th percentile climatological threshold (T95), to compute the Excess Heat Factor (EHF) for heatwave detection, which formed the basis for deriving eight key heatwave (HW) indices. These indices include the Peak of the Hottest Heatwave per Year (HWA), Average Magnitude of Yearly Heatwave (HWM), First Heatwave Day (HWT), Number of Heatwaves (HWF), Longest Heatwave Duration (HWD), Mean Duration (HWL), Peak Temperature (HWAt), and Average Heatwave Temperature (HWMt). Results show that local temperature variations influenced by latitude significantly affect heatwave intensity, especially HWA and HWM. The spatial and seasonal distribution of heatwaves across the Sahel, Savannah, and Guinea zones reveals strong linkages to climatic and geographical features. Seasonal variations in heatwave characteristics were driven by the migration of the Intertropical Discontinuity (ITD), producing four distinct seasons (DJF, MAM, JJA, and SON) across the region. The study highlights a clear increase in heatwave frequency, duration, and intensity under higher emission scenarios (SSP2-4.5 and SSP5-8.5), particularly in the far future. These trends suggest significant challenges for agriculture, water resources, and public health. The findings emphasize the urgent need for proactive adaptation and mitigation strategies to reduce vulnerability in West African communities. Ultimately, this research contributes valuable insight into the regional dynamics of heatwaves and underscores the importance of continued monitoring and climate resilience planning in the face of a warming climate.