Spatiotemporal trends in WBGT and affected population in the MENA region (1951-2021).

Rising temperatures and changes in other meteorological factors have significantly impacted human thermal comfort worldwide. Among global climate change hotspots, the Middle East and North Africa (MENA) have experienced a particularly rapid temperature rise compared to many other regions. Despite its vulnerability, long-term assessments of spatiotemporal heat stress trends and the affected population in MENA remain limited. This study evaluates changes in thermal stress using the wet-bulb globe temperature (WBGT) index derived from ERA5 meteorological data (0.25° resolution) from 1951 to 2020. The findings revealed that the average WBGT in the MENA region increased by 0.75-2.20 °C when comparing 2011-2020 with the 1951-1960 baseline. The most substantial increase occurred in the Arabian Peninsula, specifically Saudi Arabia, where the rise exceeded 0.4 °C per decade in most regions. Consequently, the annual frequency of "Normal conditions" days decreased by approximately 50 days, while high-risk and extreme heat-stress days increased by a corresponding 40 days across most of the region, particularly in the east. Significant trend analysis reveals a 10-day increase per decade across eastern and western MENA under extreme conditions. This rise has led to an additional 1.23 million people experiencing extreme heat stress for at least one day each year. The findings of this study can be useful to policymakers and researchers concerned with extreme heat in the MENA region.