WHO and global partners are calling for the protection of people’s health to be recognized as the most powerful driver of climate action, as a new global report released today warns that continued overreliance on fossil fuels and failure to adapt to a heating world are already having a devastating toll on human health.
The 2025 report of the Lancet Countdown on Health and Climate Change, produced in collaboration with the World Health Organization (WHO), finds that 12 of 20 key indicators tracking health threats have reached record levels, showing how climate inaction is costing lives, straining health systems, and undermining economies.
“The climate crisis is a health crisis. Every fraction of a degree of warming costs lives and livelihoods,” said Dr Jeremy Farrar, Assistant Director-General for Health Promotion and Disease Prevention and Care at the World Health Organization. “This report, produced with WHO as a strategic partner, makes clear that climate inaction is killing people now in all countries. However, climate action is also the greatest health opportunity of our time. Cleaner air, healthier diets, and resilient health systems can save millions of lives now and protect current and future generations.”
Key findings from the 2025 Lancet Countdown report
- Rising heat-related deaths: The rate of heat-related mortality has increased 23% since the 1990s, pushing total heat-related deaths to an average 546 000 deaths per year. The average person was exposed to 16 days of dangerous heat in 2024 that would not have been expected without climate change, with infants and older adults facing a total of over 20 heatwave days per person, a fourfold increase over the last twenty years.
- Wildfire and drought impacts: Droughts and heatwaves were associated with an additional 124 million people facing moderate or severe food insecurity in 2023.
- Economic strain: Heat exposure caused 640 billion potential labour hours to be lost in 2024, with productivity losses equivalent to US$ 1.09 trillion. The costs of heat-related deaths among older adults reached US$ 261 billion.
- Fossil fuel subsidies dwarf climate finance: Governments spent US$ 956 billion on net fossil fuel subsidies in 2023, more than triple the annual amount pledged to support climate-vulnerable countries. Fifteen countries spent more subsidizing fossil fuels than on their entire national health budgets.
- Benefits of climate action: There were an estimated 160 000 premature deaths avoided every year between 2010 and 2022, from reduced coal-derived outdoor air pollution alone. Renewable energy generation reached a record 12% of global electricity, creating 16 million jobs worldwide. Two-thirds of medical students received education in climate and health in 2024.
“We already have the solutions at hand to avoid a climate catastrophe – and communities and local governments around the world are proving that progress is possible. From clean energy growth to city adaptation, action is underway and delivering real health benefits – but we must keep up the momentum,” said Dr Marina Romanello, Executive Director of the Lancet Countdown at University College London. “Rapidly phasing out fossil fuels in favour of clean renewable energy and efficient energy use remains the most powerful lever to slow climate change and protect lives. At the same time, shifting to healthier, climate-friendly diets and more sustainable agricultural systems would massively cut pollution, greenhouse gases and deforestation, potentially saving over ten million lives a year.”
Health-promoting climate action
While some governments have slowed their climate commitments, the report shows that cities, communities and the health sector are leading the way. Nearly all reporting cities (834 of 858) have completed or plan to complete climate risk assessments. The energy transition is delivering cleaner air, healthier jobs, measurable economic growth and inward investment.
The health sector itself has shown impressive climate leadership, with health-related greenhouse gases (GHG) emissions falling 16% globally between 2021 and 2022, while improving care quality.
Data submitted by WHO show that a growing number of health systems are assessing risks and preparing for the dangerous future that's coming. Fifty-eight per cent of Member States have completed a health Vulnerability and Adaptation assessment and 60% have completed a Health National Adaptation Plan.
Looking ahead to COP30: placing health at the centre of climate action
As the world prepares for COP30 in Belém, Brazil, the findings of the 2025 Global Report of the Lancet Countdown provide a key evidence base for accelerating health-centered climate action. WHO will build on this momentum through the forthcoming COP30 Special Report on Climate Change and Health, a collaborative effort highlighting the policies and investments needed to protect health, equity, and deliver the Belém Action Plan that is the expected landmark outcome of COP30.
The Lancet Countdown on Health and Climate Change was established in partnership with Wellcome, which continues to provide core financial support. The Lancet Countdown is led by University College London, in partnership with WHO and 71 academic institutions and UN agencies worldwide. Now in its ninth year, the report provides the most comprehensive assessment of the health impacts of climate change and the co-benefits of urgent action, ahead of COP30 in Brazil.