Record heat-related deaths in 2023, WHO-partnered report finds

Record heat-related deaths in 2023, WHO-partnered report finds

The latest Lancet Countdown report in association with the World Health Organization (WHO), finds that health harms from climate change are accelerating, with expanded fossil fuel extraction holding back progress and threatening “catastrophic” health risks.

“Heat-related deaths, drought and other climate-related risks (are) increasing faster than a decade ago, even as clean energy investments and climate action begin to deliver health benefits,” the report’s authors state.

Key findings:

• Heat exposure caused the loss of 573 billion potential work hours in 2025, costed at $1.07 trillion
• Clean energy jobs grew 2.3 per cent in 2024, almost twice direct fossil fuel employment
• Cleaner air is preventing an estimated 323,000 deaths a year in 70 countries where air pollution from fossil fuels has fallen
• National laws on climate change and health have risen roughly 50-fold since the year 2000 and most have been since 2016
• Wealthy nations accounted for 55 per cent of climate–health laws in 2025, compared to two per cent in developing countries

Other findings indicate that the global area affected by extreme drought “has grown more than 700 per cent faster than it did in 2006–2015”, with droughts affecting 51.8 per cent of land on earth for at least one month in 2025.

The report also examines the link between rising temperatures and rainfall patterns to dengue transmission, finding that conditions suitable for dengue transmission by Aedes albopictus mosquitoes increased by 24 per cent between 1981-90 and 2016-25, while suitability for transmission by Aedes aegypti mosquitoes rose by seven per cent.

Drilling down

And in a warning that too little is being done to mitigate climate change, the report also notes that the world’s 100 largest oil and gas companies plan to produce “150 per cent more fossil fuels by 2040 than is compatible with keeping warming to 1.5°C [above pre-Industrial Revolution temperature averages], up from 138 per cent a year earlier”.

These and other worrying findings highlight the urgent need to formally recognize climate change as a global health emergency, the authors maintain, in support of stronger, health-centred climate action ahead of the UN COP31 climate conference in Antalya, Türkiye. 

Priorities include accelerating reductions in greenhouse gas emissions, increasing support for adaptation and expanding investments that strengthen health system resilience.

Action on climate

WHO responds to climate-related health risks through surveillance, early warning systems, health adaptation planning, technical guidance and emergency response teams.

The agency is also closely following the expected health impacts of the ongoing El Niño event through a global incident management team, mobilizing expertise, health intelligence and support to countries most at risk.

WHO also oversees the work of ATACH (the Alliance for Transformative Action on Climate and Health), the only network of health ministries and partners working together to develop climate-resilient, low-carbon and sustainable health systems at the country level.

Scientific approach

The report – produced by researchers and institutions from all over the world and led by University College London – analyses global trends across 54 indicators linking climate change and health.

It shows that heat-related deaths increased by nearly 36 per cent in the years following the 2015 Paris Agreement on climate change compared with the previous decade. The report also highlights worsening drought conditions, increasing exposure to water-related extremes and substantial economic losses linked to heat exposure.

Premature deaths protection

In more positive developments, important progress has been made in resisting the health impacts of climate change, the report notes, pointing to a record $2.1 trillion global investment in clean energy last year. 

“Many countries that have lowered fossil fuel-related air pollution are estimated to be protecting thousands of people from premature deaths each year,” it adds. 

The report also notes advances in climate-resilient health systems, including increased adoption of national health adaptation plans and climate-based early warning systems.

Around one in four countries now have a national plan for adapting health services to climate change, up from just 14 WHO Member States in 2015; 47 have separately completed a vulnerability assessment to underpin plans.

The development follows a warning by the UN World Meteorological Organization (WMO) that levels of carbon dioxide (CO2) and other major greenhouse gases accumulating in the atmosphere reached record highs in 2025, locking in more long-term temperature increase for the planet.