The World Health Organization (WHO) and The Lancet have issued a stark warning that failing to act on climate change is claiming millions of lives each year while threatening global health, economies, and livelihoods. In a joint statement on Wednesday, the organisations urged urgent recognition of health as the most powerful driver of climate action.
The warning coincides with the release of the 2025 Lancet Countdown on Health and Climate Change, produced in collaboration with WHO. The report found that 12 of 20 key indicators tracking health threats have reached record levels, highlighting the devastating impact of continued reliance on fossil fuels and inadequate adaptation to a warming planet.
“The climate crisis is a health crisis. Every fraction of a degree of warming costs lives and livelihoods,” said Dr Jeremy Farrar, WHO Assistant Director-General for Health Promotion and Disease Prevention and Care. “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.”
The report shows that heat-related mortality has increased by 23% since the 1990s, with an estimated 546,000 deaths per year. In 2024, the average person experienced 16 days of dangerous heat that would not have occurred without climate change. Extreme weather events, including droughts and heatwaves, contributed to food insecurity for an additional 124 million people in 2023.
The economic toll has been immense. Heat exposure caused the loss of 640 billion potential labour hours in 2024, equivalent to USD 1.09 trillion in productivity losses, while the financial cost of heat-related deaths among older adults reached USD 261 billion.
Governments were also criticized for continuing to spend heavily on fossil fuel subsidies, which totaled USD 956 billion in 2023, more than three times the amount pledged to support climate-vulnerable countries. Fifteen nations reportedly spent more on fossil fuel subsidies than on their national health budgets.
Despite the grim outlook, the report highlights the positive health benefits of decisive climate action. Between 2010 and 2022, reductions in coal-based air pollution prevented an estimated 160,000 premature deaths annually. Renewable energy accounted for 12% of global electricity in 2024, creating roughly 16 million jobs worldwide.
Dr Marina Romanello, Executive Director of the Lancet Countdown at University College London, stressed that solutions already exist. “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. 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.”
The report praised cities, communities, and the health sector for leading despite slowing national commitments. Nearly all reporting cities—834 out of 858—have completed or plan to complete climate risk assessments. Globally, the health sector reduced greenhouse gas emissions by 16% between 2021 and 2022 while maintaining care quality.
WHO reported that 58% of member states have completed health vulnerability and adaptation assessments, and 60% have finalized national health adaptation plans.
As the world prepares for COP30 in Belem, Brazil, the report calls for placing health at the center of global climate action. WHO announced it will release a COP30 Special Report on Climate Change and Health, detailing policies and investments needed to protect health and equity as part of the Belem Action Plan.
Now in its ninth year, the Lancet Countdown on Health and Climate Change is a collaboration between WHO, University College London, and 71 academic and UN institutions, with core support from Wellcome. It remains the most comprehensive annual assessment of the health impacts of climate change and the benefits of urgent, coordinated action.
