Lancet Countdown: over 700,000 heat-related deaths in 2023

The Lancet Countdown on Health and Climate Change 2026, published on October 28, reports that over 700,000 people died from heat in 2023: a 36% increase compared to ten years ago. The report was produced by an international team led by the Institute for Global Health at University College London, with contributions from more than 70 research centers across more than 30 countries.

This is an annual monitoring report that aggregates climate-related health indicators collected by dozens of research groups worldwide, not an experimental study on a single patient sample: the figure of 700,000 deaths represents an estimate collectively produced by the centers involved in the project, relating to the year 2023. The estimation method aggregates national mortality data and historical temperature series from the participating countries, an approach that the report itself describes as subject to margins of uncertainty depending on the quality of local monitoring systems.

The report’s authors call for climate change to be formally declared a global health emergency, a request addressed to the international institutions responsible for public health matters. The report does not specify a single body as the recipient of the appeal, but places it within the framework of international discussions on health and climate to which the Lancet Countdown has contributed every year since its first edition.

The figure of a 36% increase compared to ten years earlier places 2023 as the reference year for the historical comparison adopted by the report: an increase that the team of more than 70 research centers in more than 30 countries attributes to the temperature trends recorded that year. The report does not provide, in the summaries released so far, a geographical breakdown of the estimated 700,000 deaths, a detail that remains to be verified in the project’s forthcoming publications.