A Partial Correlation Analysis of ENSO-Driven Heatwave Severity in Burkina Faso from 2001 to 2025

Abstract

Global climate change and human activity have intensified extreme heatwaves across the West African Sahel. This study investigated the correlation between heatwave events and the El Niño-Southern Oscillation (ENSO) within Burkina Faso. This specific country is a critical study area because its atypical geography spans distinct climatic zones and is largely underrepresented in existing climatological studies. In this study, we modified the Heat Wave Magnitude Index daily (HWMId) to accurately quantify heatwave severity by extracting ERA5 2-meter maximum air temperature data to calculate daily 25th and 75th percentile thresholds from 2001 to 2025. This index was then compared against the Relative Oceanic Niño Index (RONI), a metric for measuring the magnitude of ENSO cycles that tracks sea surface temperatures. Since both ENSO and long-term global warming influence heatwaves, we included the Global Mean Surface Temperature (GMST) as a control variable in a partial correlation analysis. Through this investigation, we found the strongest relationship when RONI led heatwave conditions with an 8-month lag. At this lag, RONI had a significant positive correlation with the modified HWMId (r = 0.375, p < 0.0001). Ultimately, after accounting for global warming, ENSO explained approximately 14% of the remaining variation in heatwave severity. This analysis can serve as an early indicator for extreme heatwaves, aiding in implementing disaster response strategies.