Climate change is causing increasingly severe health damage worldwide, prompting researchers behind the 2026 Lancet Countdown to demand formal recognition of a global health emergency and stronger international action.

The assessment, published on Wednesday ahead of the COP31 climate summit, finds that deaths associated with extreme heat, exposure to drought and other climate-related dangers have increased faster than efforts to protect populations. Its authors want the World Health Organization to develop an instrument specifically addressing the prolonged health emergency created by climate change.

The tenth annual report, led by University College London and developed with WHO collaboration, examines 54 indicators. It concludes that several health threats accelerated during 2016–2025 compared with the preceding decade, despite improvements in clean energy investment, health preparedness and protective legislation.

Heat-related mortality provides one of its clearest warnings. Annual average deaths associated with heat increased by nearly 36% between the two periods. Researchers estimate that heat contributed to a record 710,000 deaths worldwide in 2023, with more than 70% of that toll attributable to human-caused climate change.

The figures are modelled estimates of heat-associated mortality and the proportion attributable to climate change, rather than counts drawn directly from death certificates. They underline the expanding burden of extreme temperatures, particularly for populations with limited access to cooling and healthcare.

Professor Marina Romanello, executive director of the Lancet Countdown, said the damage was advancing faster than the global response. She acknowledged gains from cleaner energy and stronger health systems but said those improvements remained insufficient and unevenly distributed.

The report also identifies mounting threats to food and water security. Extreme drought affected 51.8% of global land for at least one month during 2025, the second-highest proportion recorded. Shifting groundwater conditions and heavier rainfall are exposing communities to different combinations of shortages, flooding and sanitation risks.

Researchers warn that environmental conditions are becoming more favourable for mosquitoes transmitting diseases including dengue and malaria. Heat exposure also reduces workers' capacity to perform physically demanding jobs, imposing economic costs alongside the direct effects on health.

WHO Director-General Tedros Adhanom Ghebreyesus said rising heat stress, extreme weather, food insecurity and disease already demonstrated the scale of the threat. He urged governments to make health a central consideration when determining climate policies.

The proposed emergency designation would differ from WHO's existing public health emergency of international concern mechanism, which is primarily structured around extraordinary events potentially requiring coordinated international responses. Researchers argue that climate change also demands sustained preparation, financing and cross-government coordination over much longer periods.

WHO has not announced such a designation. It says existing emergency arrangements can address individual climate-related health crises and that it is working to strengthen responses through surveillance, early warnings and health adaptation planning.

The organisation has also activated emergency coordination arrangements addressing expected health impacts from the ongoing El Niño event, including support for countries facing heightened risks. Its collaboration with the Lancet Countdown includes technical work on climate change and health.

The assessment identifies substantial benefits from emissions reductions. Global clean energy investment reached $2.1 trillion in 2025, while reductions in fossil-fuel air pollution are estimated to have prevented 323,000 premature deaths annually across at least 77 countries.

Nevertheless, fossil fuels continue to supply more than four-fifths of global energy. The report estimates that production plans of the world's 100 largest oil and gas companies for 2040 exceed levels compatible with limiting warming to 1.5C by 150%, highlighting the gap between stated climate objectives and planned extraction.

Financial priorities remain another concern. Researchers estimate that 87 countries provided $808 billion in net fossil-fuel subsidies during 2024, with ten spending more on those subsidies than on their health systems. International funding earmarked for protecting health from climate hazards also remains below identified needs.

The authors recommend greater support for adaptation through grants rather than loans, particularly for countries already facing debt pressures. They also seek stronger health surveillance, accessible climate data and closer coordination between health authorities and agencies responsible for energy, finance and environmental policy.

The findings will inform discussions among governments preparing their national positions for COP31.

The report brings together 146 researchers working across more than 100 institutions in over 30 countries. Four new indicators examine terrestrial water availability, healthcare emissions assessments, climate-health research funding and legislative attention to the relationship between climate change and public health.