Heat linked to 3 million global deaths since 2016, new report finds
The Lancet Countdown urges a global health emergency declaration as climate-driven mortality outpaces policy responses.
By Nikolai Patterson ·
Global heat waves contributed to approximately 3 million deaths between 2016 and 2023, according to a report released by The Lancet. The study, published ahead of the COP31 climate summit in November, identifies these fatalities as direct consequences of climate change.
Marina Romanello, executive director of the Lancet Countdown, stated that harmful health effects from climate change are advancing faster than the global response. She called for nations to recognize climate change as a global health emergency. This designation would allow governments to create an emergency intervention device similar to the mechanism the World Health Organization used during pandemics.
The report covers the period from the entry into force of the Paris Agreement in 2016 through 2023, the final year with complete data. In 2023 alone, 710,000 deaths were associated with heat. This figure exceeds mortality from malaria or HIV. Researchers estimate that more than two-thirds of these 2023 deaths are attributable to human-caused climate change.
Ollie Jay, a professor at the University of Sydney, explained the methodology. The team calculated the difference between recorded heat deaths and projected deaths in a scenario without climate change. He noted that while hot periods have always existed, human-caused warming has amplified their intensity and frequency.
The economic toll is substantial. The report estimates that reduced worker productivity cost the global economy one trillion dollars annually over the last three years. Southeast Asia and Africa suffered the largest losses, with productivity drops equivalent to 3.9% and 3.2% of their GDP, respectively. Europe lost 0.2% of its GDP, while the Americas lost 1.5%.
Despite progress in 56 countries that have adapted their health systems, air pollution from fossil fuels still causes 2.73 million deaths per year. Fossil fuels account for 80% of global energy. In 2025, clean energy investments reached $2.1 trillion, double the amount spent on fossil fuels. However, in 77 countries that reduced fossil fuel pollution since 2016, an estimated 323,000 deaths were avoided.
Research funding for climate-related medical studies has increased sevenfold, but 84% of the $316 million allocated in 2024 went to researchers in wealthy nations. Romanello described the current efforts as too slow and too modest, arguing they do not benefit those who need them most. She added that geopolitical instability has pushed climate health impacts to the background in recent years.
