Record Heat Deaths Drive Global Health Emergency Call

Heat deaths reached a record in 2023, when heat was linked to seven hundred and ten thousand fatalities worldwide, according to the 2026 Lancet Countdown on Health and Climate Change. More than 70% of that toll was attributed to human-caused climate change, and the report's authors are calling for climate change to be formally recognised as a global health emergency ahead of COP31, the United Nations climate conference.

The tenth annual edition of the Countdown, led by University College London and developed in strategic collaboration with the World Health Organization (WHO), draws on 146 researchers from more than 100 institutions across more than 30 countries. It tracks 54 indicators linking climate change and health, and its central finding is that many harms grew faster in the decade after the Paris Agreement entered into force than in the decade before it.

Annual average heat-related fatalities rose by nearly 36% in the years after the Paris Agreement compared with the previous decade, the report found. Across the eight years that followed the agreement, the researchers estimate that climate change caused almost three million heat-related fatalities. The toll in the record year alone exceeded deaths from malaria or HIV, according to the report's summary.

Why the authors want an emergency declaration

Under the International Health Regulations, a public health emergency of international concern is an extraordinary event that poses a public health risk to other states and may require a coordinated international response. In a commentary published in The Lancet, researchers led by Nicholas Brink argued that the climate crisis meets most, if not all, of the criteria for such a declaration, and said any further delay would cost lives that could have been prevented. The call has drawn support from health ministries in Africa, including Senegal, Namibia and Zimbabwe, according to the commentary.

WHO has not made the declaration, but the agency said it is using existing instruments to respond to climate emergencies in line with the report's recommendations. Since September, WHO has run a graded emergency response to the expected health effects of the ongoing El Niño event, mobilising expertise and support for the countries most at risk through a Global Incident Management Team. Dr Diarmid Campbell-Lendrum, head of WHO's climate change, air quality and energy and health unit, said: "Climate change is already harming health in every region of the world, and the evidence shows that many of these impacts are accelerating."

Older adults, pregnant women, children and people living with chronic illness face the greatest risk, the researchers said, while communities in the Global South bear the heaviest burden despite contributing least to the problem. The risks to children were also at the centre of a youth climate trial. For those communities, the report's authors said, climate change means failed crops, clinics cut off by floods and disease seasons that arrive earlier and last longer.

The toll on workers and economies

Exposure is rising alongside the fatality count. The average person lived through 13.6 heatwave days in 2025, and 11.3 of those days would not have occurred without climate change, the Countdown found. The warming trend continued into October, reported as the hottest October on record. Heat cost workers 573 billion potential labour hours last year, worth roughly US$1.07 trillion in lost potential income, or about 1% of global economic output. The average worker lost 159 potential labour hours to heat.

There are signs of movement in the opposite direction. Global investment in clean energy reached a record US$2.1 trillion, and countries that have lowered fossil fuel-related air pollution are estimated to be protecting thousands of people from premature death each year, according to the report. Adoption of national health adaptation plans and climate-informed early warning systems has also increased, giving communities more warning before extreme weather arrives.

What happens next

The report's authors want health placed at the centre of climate policy as countries prepare for the November conference, with health considerations built into decisions on cutting emissions, adapting to impacts and financing the response. Their priorities include faster reductions in greenhouse gas emissions, more support for adaptation and greater investment in health systems that can withstand heat, floods and shifting disease patterns. The WHO has published its summary of the findings, and the Countdown's indicators are described in coverage of the report.