Missed Reports of Extreme Heat Events Exacerbate Vulnerability and Losses

Climate risks are systematically under-observed in the world’s most vulnerable regions, compounding exposure by delaying preparedness and adaptation. Using 2.1 million news articles across 184 countries and 40 languages, combined with AI-assisted geolocation and human-in-the-loop validation, we expose global under-reporting of extreme heat events. We find that only a tiny fraction of identified extreme heat events enters widely used global disaster databases, while 63.38% remain unreported even across the most comprehensive global and local news coverage. Under-reporting is concentrated in places like equatorial Africa, the Amazon basin, small island states, such as the Caribbean, and polar adjacent regions, where limited early warning capacity, high vulnerability, and linguistic distance from dominant languages intersect. Under the high-emissions scenario SSP5-8.5, by 2050, the largest future heat burdens are concentrated in highly vulnerable countries that coincide with the most severe under-reporting of extreme heat. These countries are projected to incur economic losses 60.09% higher and mortality-related losses 46.40% higher than better-reported countries. Yet pervasive under-reporting suggests that even these severe loss projections remain conservative for regions with the highest vulnerability, reinforcing the urgency of loss-and-damage action.