Lancet Countdown 2025 reveals delayed climate action and reliance on fossil fuels is fuelling deaths, disease and economic loss
The 2025 Lancet Countdown on Health and Climate Change reveals that climate inaction and continued dependence on fossil fuels is resulting in an immense human cost, with millions of lives lost each year due to heat, air pollution, disease spread, and worsening food insecurity.
The report, led by University College London (UCL) and produced in collaboration with the World Health Organization (WHO), the London School of Hygiene & Tropical Medicine (LSHTM), and 70 other academic institutions and UN agencies, warns that the health and economic consequences of delayed climate action are escalating rapidly.
This is the ninth Lancet Countdown report and this year includes new metrics on the impacts of extreme heat and wildfire smoke, urban blue spaces (rivers, lakes and coastlines), and funding. These indicators highlights where things are getting worse or improving, and where urgent action is needed.
The latest findings reveal that 12 of 20 key health indicators have reached unprecedented levels, as the world's failure to curb emissions and adapt to climate impacts intensifies threats to health and livelihoods worldwide.
The rate of heat-related deaths has risen by 23% since the 1990s (taking into account population growth) reaching an average of 546,000 annual deaths between 2012 and 2021.
The year 2024 was the hottest on record, with the most vulnerable (those under 1 and over 65 years) exposed to more than 300% additional heatwave days on average, compared with the annual average between 1986 and 2005.
Hotter and drier conditions exacerbated the risk of wildfires with implications for health - in 2024 alone, wildfire smoke pollution was associated with a record 154,000 deaths. Extreme rainfall (which can trigger flash floods and landslides) and droughts increased in over 60% of the world's land surface. These extremes of heat, rainfall and droughts affect crop productivity, disrupt supply chains, and threaten food security.
Changing climates also affect the risk of transmitting deadly infectious diseases - indicators in the report found the potential for dengue transmission has climbed by nearly 50% globally since the 1950s.
Delays in the adoption of clean, climate-friendly energy and the continued burning of fossil fuels not only heats the planet, but produces dangerous air pollution, resulting in millions of additional deaths per year. In the UK, air pollution caused 28,000 premature deaths in 2022 - 55% of which came from fossil fuel burning.
Unsustainable food systems with high-carbon, unhealthy diets contributed to 11.8 million diet-related deaths worldwide in 2022, which the authors say could largely be avoided by transitioning to healthier, climate-friendly food systems.
The report highlights that the failure to transition away from fossil fuels also takes a toll on the economy, with the health impacts of climate change resulting in reduced productivity, more time off work, and an increased burden on health systems.
In 2024, heat exposure resulted in a record 639 billion potential hours of lost productivity, with income losses equivalent to USD $1.09 trillion (around £824 billion) - almost 1% of global GDP. In the UK, over 5 million potential labour hours were lost due to extreme heat exposure, resulting in a potential income loss of $103 million (£77.9 million).
Meanwhile following a rise in fossil fuel prices, governments collectively spent $956 billion (£723 billion) in net fossil fuel subsidies in 2023 to keep energy locally affordable, more than triple the commitment pledged to support vulnerable countries at COP29.
Despite some governments rolling back climate commitments, the report finds positive change at local and sectoral levels, and climate change action is already delivering health and economic benefits.
The health sector's greenhouse gas emissions fell 16% globally between 2021 and 2022, and renewable energy generation has reached record highs. An estimated 160,000 premature deaths are prevented each year due to reduced coal use and cleaner air, particularly in high income countries.
The authors stress that solutions to avert further harm are already available, with cleaner energy, resilient health systems, and sustainable food systems offering immediate and long-term health gains.
Dr James Milner, Associate Professor in Climate Change, Environment & Health at LSHTM and co-author on the report said: "The latest Lancet Countdown report shows that the world remains well off-track in its efforts to prevent climate change. The gap between global greenhouse gas emissions and the reductions needed to meet the goals of the Paris agreement has continued to grow.
"Despite this, the report also demonstrates that there are unprecedented opportunities for us to tackle the climate crisis while improving people's health at the same time, through actions including transforming energy systems, improving access to clean household fuels, and shifting to low carbon transport."
Tafadzwa Mahbhaudi, Professor of Climate Change, Food Systems and Health at LSHTM and Director of the Lancet Countdown Africa said: "Climate change action remains one of the greatest health opportunities of the 21st century, also driving development, spurring innovation, creating jobs, and reducing energy poverty. Realising the myriad benefits of a health-centred response requires unlocking so-far untapped opportunities to mitigate climate change and build resilience to the impacts already being felt."
