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Premature deaths are linked to air pollution, extreme heat, and other consequences of fossil fuel use.
University College London (UCL), in partnership with the WHO, has been monitoring climate change, countries’ responses, and impacts on human health for the ninth consecutive year. The study involves an international, multidisciplinary team. The latest report shows that health threats have reached unprecedented levels, according to Phys.org.
The annual monitoring project is called The Lancet Countdown on Health and Climate Change. Founded by The Lancet, one of the world’s oldest and most respected medical journals, it is coordinated by UCL. The WHO provides global data access and methodological guidance, ensuring the report’s use in policy and lending international legitimacy to the research.
Each year, experts analyze climate change impacts on human health across 20 indicators. In 2025, 12 indicators reached record levels of harm. Compared to the 1990s, heat-related mortality has risen by 23%, now causing 546,000 premature deaths annually. Another indicator is dengue fever, transmitted by mosquitoes.
Dengue can be severe, causing internal bleeding and hemorrhagic shock, as the virus damages capillary walls. While the disease is historically confined to regions with carrier mosquitoes, global warming has expanded their range. Consequently, dengue serves as a climate change indicator. The global transmission potential of dengue has increased by 49% since the 1950s.
Air pollution is another major driver of premature death. The study examined emissions from fossil fuel combustion and wildfires. Fossil fuel pollution alone causes 2.5 million deaths per year. Wildfires in 2024 caused 154,000 deaths—a record high. The number of fires in 2024 was also unprecedented. These figures include both direct deaths (from heatstroke or smoke inhalation) and deaths from diseases triggered by climate change.
Researchers stress that today’s trends result from slow government and industrial responses to a growing global threat. Global climate policies are only partially effective. Analysis by The Conversation indicates that international efforts under the Paris Agreement have avoided the worst-case scenario of total ecological collapse, but severe risks remain. Humanity has the technological capacity to address the crisis—it lacks only awareness of the urgency and the political will to implement radical change.
