Global Health: Heat Claims 3 Million Lives

Heat killed an estimated 3 million people worldwide between 2016 and 2023, according to a new report published by the medical journal The Lancet. The study, released ahead of the COP31 climate summit in November, argues that governments must treat climate change as a global health emergency. It calls for an urgent intervention mechanism similar to the one the World Health Organization used during the pandemic.

The report marks the 10th edition of the Lancet Countdown on health and climate change. It involves 146 researchers from 30 countries who assessed how changing weather patterns affect global population health. Marina Romanello, the executive director of the Lancet Countdown, stated that the damaging effects of climate change on health are advancing faster than the world's response. She noted that these effects are even accelerating.

The analysis covers the period from 2016, when the Paris Agreement took effect, through 2023, the last year with complete data. The Paris Agreement aimed to limit global warming to 1.5 degrees Celsius above pre-industrial levels. During this eight-year span, researchers linked nearly 3 million deaths to heat. In 2023 alone, a record 710,000 deaths were associated with heat, exceeding the number of deaths from malaria or HIV. More than two-thirds of these deaths were attributable to human-caused climate change.

Professor Ollie Jay from the University of Sydney explained the methodology. The researchers calculated the difference between actual heat-related deaths and those that would have occurred in a scenario without climate change. He noted that while hot periods always exist, their intensity and frequency are amplified by human activity, leading to more deaths than expected.

The economic impact is also substantial. The report states that heat reduced worker productivity, costing the global economy one trillion dollars per year over the last three years. Southeast Asia and Africa suffered the most, with productivity losses equal to 3.9% and 3.2% of their GDP, respectively. In comparison, Europe lost 0.2% and the Americas lost 1.5%.

The report identifies some progress since 2016. Fifty-six of the 194 World Health Organization member countries have adapted their health systems, and early warning systems for extreme weather have been established. Investment in clean energy reached 2.1 trillion dollars in 2025, doubling spending on fossil fuels. However, fossil fuels still account for 80% of the world's energy and cause air pollution that kills 2.73 million people annually. In 77 countries where fossil fuel pollution has decreased since 2016, about 323,000 deaths have been avoided.

Research funding for climate-related medical topics has grown sevenfold. Yet, 84% of the 316 million dollars spent on this research in 2024 went to researchers in wealthy nations, even though less developed countries face the greatest health threats. Romanello described current efforts as too slow and too modest, noting they do not benefit those who need them most. She added that global geopolitical instability has pushed climate change and its health impacts to the background.