Global Heat Claims Three Million Lives

A report published by the British medical journal The Lancet on Wednesday states that heat linked to climate change caused approximately three million deaths worldwide between 2016 and 2023. The study, released ahead of the COP31 climate summit scheduled for November, calls for an official declaration of a global health emergency. Marina Romanello, the executive director of the Lancet Countdown, noted that harmful health effects are advancing faster than the world is responding. She added that these effects are even accelerating, which is why the report asks for immediate recognition of the crisis.

The analysis covers the period from the implementation of the Paris Agreement in 2016 through 2023, the most recent year with complete data. In 2023 alone, researchers attributed 710,000 deaths to heat. This annual figure exceeds the number of deaths from malaria or HIV. More than two thirds of those heat related deaths in 2023 are directly attributable to human made climate change, according to the study.

Ollie Jay, a professor at the University of Sydney, explained how the researchers calculated these figures. The team compared recorded heat deaths with a hypothetical scenario where climate change did not exist. Jay stated that while heat waves are natural, their intensity and frequency are amplified by human activity. This amplification results in more deaths than would have occurred otherwise.

The report also details the economic impact of rising temperatures. Workers lose productivity as heat intensifies, costing the global economy one trillion dollars annually over the last three years. Southeast Asia and Africa are the most affected regions, with productivity losses equal to 3.9 percent and 3.2 percent of their respective gross domestic products. By comparison, the loss in Europe is 0.2 percent, and in the Americas, it is 1.5 percent.

Despite the rising toll, the study identifies real 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 events have been established. Investments in clean energy reached 2.1 trillion dollars in 2025, doubling the amount spent on fossil fuels. However, fossil fuels still account for 80 percent of global energy and cause 2.73 million deaths per year from air pollution.

In 77 countries that reduced fossil fuel related pollution since 2016, an estimated 323,000 deaths were avoided. The report notes that funding for climate related medical research has multiplied sevenfold. Yet, 84 percent of the 316 million dollars dedicated 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, arguing that they do not benefit those who need them most. She also noted that geopolitical instability has pushed the health impacts of warming to the background in recent years.