Mortality associated with non-optimal ambient temperatures from 2000 to 2019

- A 2021 *Lancet Planetary Health* study estimating global deaths linked to non-optimal temperatures (too hot or too cold) between 2000 and 2019. It used data from 750+ locations in 43 countries. - Key finding: roughly 5 million excess deaths per year were attributable to non-optimal temperatures. Cold accounted for the vast majority (~8–9% of all deaths), heat for about 0.9–1%. Even in a warming world, cold remains the bigger killer. - The "minimum mortality temperature" is the temperature at which death risk is lowest; deviations in either direction (cold or hot) are considered non-optimal. The study models how far each location's daily temperatures deviate from this optimum. - Why it matters: climate change discussions often focus on heatwaves, but this research shows cold-related mortality is also a major public health burden. It helps governments and health agencies design balanced adaptation strategies—better housing insulation and cold warning systems, not just heat action plans. Regions like South Asia, Eastern Europe, and sub-Saharan Africa are especially vulnerable.