A diverse team of scientists from leading public health institutions has demonstrated that extremely hot nights driven by climate change could push global mortality higher, potentially by about 60% by the end of the century. The findings appear in a major health journal focused on planetary health and climate impacts.
Drawing on mortality and temperature data from 28 East Asian cities, climatologists project that by 2100 the toll of heat could rise substantially due to higher nighttime temperatures and more frequent extremely hot nights. The study estimates that nighttime temps could rise from an average around 20.4℃ to roughly 39.7℃, nearly doubling in some periods, while the occurrence of hot nights would climb by more than 30%. In comparison, the average daytime temperature is expected to rise by less than 20%. This suggests that deaths linked to nocturnal heat may outpace those linked to daytime warming, underscoring the stronger health risk posed by nighttime heat than previously understood.
When room temperatures stay elevated during the night, sleep quality declines and sleep disorders may intensify. Sleep disruption is linked to immune system issues and a higher risk of cardiovascular disease and other health problems. The implication is clear: nighttime temperature should be a central consideration in designing future heatwave warnings, particularly to protect vulnerable populations and households with limited means to access cooling solutions in hot conditions.
The researchers caution that results are based on data from 28 cities in three countries, which means care is needed when generalizing these projections to broader regions in East Asia or other parts of the world. Plans are in place to test the findings against a larger, global dataset to improve confidence in regional applicability and policy guidance.
The project brings together expertise from several universities and research centers across Asia, Europe, and North America, underscoring a collaborative approach to understanding climate-related health risks. The involvement of institutions in Shanghai, Seoul, Tokyo, and beyond highlights the international scope of climate health research, while cross-continental collaboration aims to translate insights into practical resilience measures for cities in Canada and the United States as well as other regions with similar social and economic patterns.
In summary, the work emphasizes a shift in how heat risk is evaluated. Nighttime heat is not a mere companion to daytime heat; it is a distinct factor with significant consequences for public health. The study calls for integrating nocturnal temperature metrics into heat warning systems, public advisories, and urban planning strategies. By anticipating higher night-time heat exposure, policymakers can better protect communities that are most at risk, including low-income households and seniors, and ensure that adaptation measures are both timely and effective. Marked citations acknowledge the research’s source and its authors’ institutions, reflecting the collaborative, global effort to safeguard health as climate conditions intensify.