Lancet Countdown: Nearly 3 million heat deaths linked to climate change
The 10th Lancet Countdown report, led by UCL with the WHO, finds more drought and growing heat impacts. The authors urge that the climate crisis be recognized as a global health emergency.
Symbolic image · Photo: NASA Earth Observatory images by Lauren Dauphin and Joshua Stevens, using MODIS data from LANCE/EOSDIS Rapid Response an / Wikimedia Commons, Public domain (cropped and resized)
The health harms of climate change are growing faster than the world's response, according to the 10th report of the Lancet Countdown, published in the medical journal The Lancet. The work is led by University College London (UCL) with the World Health Organization and involves 146 researchers from more than 100 institutions. Based on the authors' model estimates, heat was linked to an average of about 540,800 deaths a year from 2016 to 2023. They attribute 68% of these to climate change, up from 55% in 2006–2015.
In total, the report attributes nearly 3 million heat deaths in 2016–2023 to climate change. These are statistical estimates, not counted cases. Measured data show that in 2025, 51.8% of the world's land experienced at least one month of extreme drought. The share of land hit by very heavy rainfall rose from 14.8% to 17.2% a year. The authors put income losses from heat-reduced labor at $1.07 trillion in 2025.
There are also positive trends: clean energy investment hit a record $2.1 trillion in 2025, well above investment in fossil fuels. Cleaner air prevents about 323,000 deaths a year in at least 77 countries, the report says. The trend is "a step change that must be recognized as the global health emergency it is," said Marina Romanello of UCL, executive director of the Lancet Countdown.