Overview

• Scientists report that human-caused warming exposed four billion people to at least 30 extra days of extreme heat between May 2024 and May 2025.
• Regions closest to the equator, including Indonesia, Singapore, Barbados and Haiti, saw the steepest increases in heat days, with some locations recording over 120 additional days.
• Under a 1.5 °C warming scenario, 52% of those born in 2020 will face unprecedented lifetime heatwave exposure, compared to just 16% of the 1960 cohort.
• Low-income communities, older adults and people with medical conditions suffer the most severe health impacts as energy grids and healthcare systems strain under rising temperatures.
• Researchers call for a rapid phase-out of fossil fuels alongside early warning systems, urban heat action plans and resilient infrastructure to mitigate escalating heat risks.