WHO and global partners have urged that protecting human health be recognized as a key driver of climate action. A new global report warns that the world’s continued dependence on fossil fuels and slow adaptation to rising temperatures are already inflicting severe health impacts.
The 2025 Lancet Countdown on Health and Climate Change report, released in collaboration with the World Health Organization (WHO), reveals that 12 out of 20 key health indicators have hit record highs — underscoring how climate inaction is claiming lives, overwhelming health systems, and threatening economic stability.
“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 Highlights from the 2025 Lancet Countdown Report
Rising heat-related deaths: Heat-related mortality has surged by 23% since the 1990s, averaging 546,000 deaths annually. In 2024, people experienced an average of 16 days of dangerous heat that wouldn’t have occurred without climate change. Infants and older adults were hit hardest, facing over 20 heatwave days each—a fourfold increase in two decades.
Wildfire and drought impacts: Droughts and heatwaves in 2023 left 124 million additional people facing moderate to severe food insecurity.
Economic strain: Heat exposure led to the loss of 640 billion labour hours in 2024—valued at US$ 1.09 trillion—while heat-related deaths among older adults cost US$ 261 billion.
Fossil fuel subsidies vs. climate finance: In 2023, governments spent US$ 956 billion on fossil fuel subsidies—three times the amount pledged for climate aid. Notably, 15 countries spent more on fossil fuels than on their entire national health budgets.
Benefits of climate action: Between 2010 and 2022, reduced coal-related air pollution prevented an estimated 160,000 premature deaths annually. Renewable energy reached a record 12% of global electricity, generating 16 million jobs, while two-thirds of medical students worldwide received training on 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
Despite some governments slowing their climate commitments, the report highlights strong leadership from cities, communities, and the health sector in driving health-focused climate action. Nearly all reporting cities — 834 out of 858 — have completed or plan to conduct climate risk assessments. The ongoing energy transition is delivering cleaner air, healthier employment opportunities, economic growth, and increased investment.
The health sector has also emerged as a key climate leader, reducing greenhouse gas emissions by 16% globally between 2021 and 2022, while simultaneously enhancing the quality of care. According to WHO data, an increasing number of countries are preparing their health systems for future climate threats — 58% of Member States have completed a Health Vulnerability and Adaptation Assessment, and 60% have finalized a Health National Adaptation Plan.
Looking Ahead to COP30: Putting Health at the Core of Climate Action
As the world gears up for COP30 in Belém, Brazil, the 2025 Lancet Countdown Global Report serves as critical evidence for accelerating health-centered climate strategies. WHO aims to build on this momentum through its COP30 Special Report on Climate Change and Health, which will outline key policies and investments to safeguard health, promote equity, and implement the Belém Action Plan — the anticipated hallmark of COP30.
Established in collaboration with Wellcome, which continues to offer core financial support, the Lancet Countdown on Health and Climate Change is led by University College London (UCL) in partnership with WHO and 71 academic institutions and UN agencies worldwide. Now in its ninth year, it remains the most comprehensive assessment of how climate change impacts health — and the powerful co-benefits of urgent climate action.