Assessing the Dynamics of Heatwaves over the Sahel Region of West Africa: Characterization and Projections

Abstract

This study investigates the historical trends and future projections of heatwaves over the Sahel region of West Africa, a climate-sensitive and socioeconomically vulnerable area. Utilizing ERA5 reanalysis data (1984–2014) and statistically downscaled outputs from 11 CMIP6 models under SSP2-4.5 and SSP5-8.5 scenarios, the study examines five heatwave metrics (frequency, number, duration, amplitude, and magnitude) across three heatwave definitions (TX90, TN90, EHF). The results confirm that the Sahel is experiencing intensifying heatwave events. Historically, daytime heatwaves (TX90) show higher frequencies (1.0–1.9 events/year), while nighttime heatwaves (TN90) reveal significant positive trends in frequency and duration, especially in the northern zones. The Excess Heat Factor (EHF) underscores the growing intensity and compound impact of heat extremes. Model validation using Taylor diagrams and Mann-Kendall trend tests confirms the robustness of projections despite biases among models. Future projections reveal alarming trends. By 2091, under SSP5-8.5, HWF could exceed 25 days/year, with amplitude values surpassing 50°C in parts of the central Sahel. These findings suggest a severe escalation in heat-related health risks, especially due to rising nighttime temperatures that limit physiological recovery. The study confirms the hypothesis that heatwaves in the Sahel are intensifying and are expected to worsen under future climate scenarios. This research provides vital input for developing region-specific early warning systems and adaptation plans. It highlights the urgency of strengthening climate resilience in the Sahel through enhanced forecasting, infrastructure planning, and health interventions.