Lancet Countdown: heat linked to 710,000 deaths in 2023, health emergency status requested

The Lancet Countdown on Health and Climate Change 2026 was published on Wednesday, 28 October by a working group led by University College London, which brings together over one hundred institutions in more than thirty countries.

The report estimates that in 2023 heat was associated with 710,000 deaths worldwide. Of these, the authors attribute over 70 percent to human-caused climate change: an estimate built by comparing climate scenarios with and without human influence, not a direct case-by-case measurement, and which should therefore be read as a statistical attribution of a share of the phenomenon, not as a certain count of individual causes.

According to the report, the annual average of heat-related deaths has increased by almost 36 percent globally since the Paris Agreement came into force. The method used compares 54 different indicators between the decade 2016-2025 and the previous one, 2006-2015, finding that many climate-related health impacts have worsened more rapidly in the more recent period.

Based on this data, the authors call for the formal recognition of climate change as a global health emergency, and the systematic integration of health into decisions on mitigation and climate finance. The report’s executive director summarised the request as follows:

“Health must be at the centre of every climate decision” — Marina Romanello, executive director of the Lancet Countdown

The report is based on a comparison between two decades of indicators and not on a single episode: the robustness of the estimate on attributable deaths therefore depends on the quality of the models used to separate the climate effect from other factors of heat-related mortality, a methodological limitation intrinsic to this type of comparative analysis.