Climate Change and Health
How climate change is emerging as the greatest threat to global health in the 21st century, from heat deaths and vector-borne diseases to food insecurity and mental health.
The Health Impacts
The WHO has called climate change the greatest threat to health in the 21st century. The pathways from climate change to health harm are numerous. Rising temperatures increase heat-related mortality: the 2023 European heatwave caused an estimated 60,000 excess deaths. Changing rainfall patterns expand the range of mosquito-borne diseases like malaria and dengue into previously unaffected regions. Air pollution from wildfires, intensified by climate change, causes respiratory disease. Food insecurity, driven by drought and crop failure, threatens nutrition for hundreds of millions.
The Lancet Countdown, an annual assessment of health and climate change, tracks multiple indicators. It has documented increasing heat exposure for vulnerable populations, expanding suitability for disease vectors, declining crop yield potential, and growing economic losses from extreme weather. The health impacts are disproportionately felt by populations that contributed least to emissions: subsistence farmers in the Sahel, slum dwellers in South Asian cities, and indigenous communities worldwide.