Uninhabitable cities: urban temperatures outside the climate niche in 2100

This study evaluates the projected impacts of future temperature increases on urban populations across 1,500 cities with over 300,000 inhabitants globally. By integrating downscaled climate data, population projections, and urban morphology, we identify cities at risk of surpassing the 29°C threshold of mean annual temperature, marking the upper limit of the human climate niche. Under three climate scenarios (SSP126, SSP370, and SSP585), our projections for 2100 suggest that 29 cities (SSP126) to 215 cities (SSP585), housing approximately 60 million (SSP126) to 446 million (SSP370) people, may exceed this critical threshold. These findings underscore the challenges for urban livability, particularly in regions such as Africa, South America, and Asia.