A new report from The Lancet reveals that climate change is already killing millions annually, with extreme heat claiming one life every minute. The 2025 Countdown on Health and Climate Change warns of eroding public health gains amid rising temperatures and environmental threats. As leaders prepare for COP30 in Brazil, the findings underscore the urgent need for action.
The British medical journal The Lancet released its annual “Countdown on Health and Climate Change” report on October 31, 2025, compiled by global researchers since 2015. This year's edition builds on a 2020 warning that climate change could “undermine the past 50 years of gains in public health,” stating that such erosion is now underway. “Climate change is increasingly destabilising the planetary systems and environmental conditions on which human life depends,” the authors wrote.
Key findings highlight extreme heat's deadly toll: it now kills one person every minute, with heat-related deaths up 23 percent since the 1990s, largely due to fossil fuel-driven warming. The vast majority of heatwave days from 2020 to 2024 would not have happened without climate change. Wildfire smoke deaths rose 36 percent in 2024 compared to the 2003-2012 baseline, while droughts and heatwaves contributed to 124 million additional cases of moderate or severe food insecurity in 2023 versus the 1981-2010 average. Infectious diseases like dengue fever are also spreading more widely.
The report tracks 20 health indicators, including air pollution, food insecurity, and extreme weather; 13 worsened over the past year. Harjeet Singh, founding director of the Satat Sampada Climate Foundation, called it “a devastating global health audit,” adding, “Our fossil fuel addiction is killing us by the millions.”
Attributing health effects to climate change remains challenging due to intertwined factors like behavior and urban sprawl, but the report synthesizes global research to clarify these links. As world leaders head to COP30 in northern Brazil, the authors critique inaction: “Paradoxically, as the need for decisive health-protective action grows, some world leaders are disregarding the growing body of scientific evidence on health and climate change.” This includes the United States beginning withdrawal from the Paris agreement and World Health Organization under President Donald Trump.