A new study warns that, by 2050, extreme heat could expose almost half of the world’s population to dangerous conditions — and that global preparedness is inadequate. The analysis projects marked increases in heatwave frequency and intensity, with disproportionate impacts on urban populations, workers, older people and lower-income communities, creating risks for health, wellbeing, labour productivity, displacement and sustainability. Authors call for urgent mitigation (deep emissions cuts) alongside targeted adaptation: heat-resilient infrastructure, equitable access to cooling and water, early-warning systems and planning to reduce inequitable risks.