The evidence that climate change threatens human health has never been stronger. Yet a new report suggests that world leaders are giving less attention to its health consequences in international political debate.

The 2026 Lancet Countdown report estimates that heat was associated with 710,000 deaths worldwide in 2023, with around 71% attributable to human-caused climate change. Researchers calculated this by comparing estimated heat-related deaths at the temperatures actually experienced with those expected in a world without human-caused warming. The difference represents the additional deaths associated with climate change.

Heat can cause fatal heatstroke and worsen existing conditions, including heart and kidney disease. The figure is a statistical estimate of the additional deaths caused by warming, rather than a count of individual deaths directly identified as resulting from climate change.

Meanwhile, the proportion of countries whose leaders discussed the relationship between climate change and health during the United Nations General Debate fell from 66% in 2021 to 26% in 2025. The General Debate is the annual gathering at which world leaders address a broad range of international issues.

Europe’s record-breaking heatwaves during the summer of 2026 brought the consequences of rising temperatures into sharp focus. Research examining 854 European cities estimated more than 50,000 heat-related deaths that summer, with around two-thirds attributable to........

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