Heat linked to over 700,000 global deaths in 2023, study estimates

**Lead**

A new global study has estimated that high temperatures were linked to more than 700,000 deaths in 2023, making it one of the deadliest years for heat-related mortality on record. The research, which analysed temperature and mortality data from over a hundred countries, is among the most comprehensive assessments of the health impact of extreme heat to date.

**Context**

The study, conducted by an international team of climate and health scientists, examined mortality records alongside detailed temperature anomalies, employing statistical models to separate heat-related deaths from other causes. The findings suggest that prolonged periods of elevated temperatures in 2023 – a year marked by successive heatwaves across Europe, Asia and the Americas – contributed to an estimated death toll exceeding 700,000. This figure mirrors or surpasses similar estimates from prior high-temperature years, signalling a worrying upward trend as the planet continues to warm.

The worst-affected regions included southern Europe, South Asia and parts of Latin America, where extreme heat persisted for weeks and strained medical services. Vulnerable groups, including older adults, outdoor labourers and individuals with chronic respiratory or cardiovascular conditions, were disproportionately represented in the mortality data. The authors emphasised that the true number of heat-related deaths could be even higher, given difficulties in attributing deaths to temperature in developing countries with less comprehensive health records.

The study also underscored the role of climate change in escalating heat risk. Global average temperatures in 2023 were confirmed by the World Meteorological Organization to be the highest ever recorded, with episodes of exceptional heat in July and August. While natural climate variability such as El Niño played a part, the researchers noted that the underlying warming trend caused by greenhouse gas emissions made these temperatures far more likely and severe. The World Meteorological Organization separately noted that 2023 saw unprecedented ocean heat, which contributed to extreme conditions over land.

**Analysis**

The findings have profound implications for public health systems, particularly in countries that have historically been less prepared for extreme heat. In the United Kingdom, where temperatures are rising but health infrastructure is not yet fully adapted to sustained heatwaves, the research serves as a crucial warning. Although the UK does not typically experience the same extremes as southern Europe, the 2022 heatwave caused thousands of excess deaths and disrupted transportation and healthcare. The 2023 study suggests that without enhanced adaptation measures, the UK could face a growing number of heat-related deaths as summers become hotter and more unpredictable.

The research also highlights important global disparities. Many of the regions most exposed to extreme heat are also those with the least capacity to adapt, lacking robust early warning systems, affordable healthcare and shade infrastructure. This reinforces the need for international cooperation on climate adaptation and emissions reduction. At the same time, the findings provide a stark reminder that extreme heat is not just an inconvenience but a lethal public health emergency. Health services need to plan for surges in hospital admissions during heat events, implement cooling centres and community outreach programmes, and ensure that urban design incorporates green space and reflective materials to mitigate the urban heat island effect.

For policy-makers, the study offers a compelling argument for treating heat as a priority on par with other climate-related hazards like floods and storms. It also strengthens the case for rapid decarbonisation: every fraction of a degree of warming avoided could translate into tens of thousands of lives saved. The researchers have called for revised heat-health action plans, better data collection, and greater investment in climate-resilient healthcare. The evidence is unequivocal – heat is now one of the deadliest consequences of a changing climate, and further inaction will come at a staggering human cost.

**Sources**

The study on high temperatures and global mortality, published in a peer-reviewed scientific journal. Additional data from the World Meteorological Organization on global temperatures and extreme weather events in 2023.