Climate change must be declared a global health emergency to shape government policies after heat caused three million deaths between 2016 and 2023. A report published by The Lancet on Wednesday made the warning ahead of the COP31 climate summit in November.
The tenth edition of the report brought together 146 researchers from 30 countries to assess the impact of climate change on population health. It recorded 710,000 heat-related deaths in 2023 alone. More than 70 percent of that total was linked to human-caused climate change.
Marina Romanello spoke at a news conference on Wednesday. She is the executive director of the Lancet Countdown project, and she said there were three million heat-related deaths globally in an eight-year span since the Paris Agreement of 2015.
That is roughly equivalent to the entire population of Wales being wiped out in the space of eight years due to heat. Romanello stated that 68 percent of those deaths are directly attributable to climate change. The legally binding international climate treaty adopted in Paris aimed to limit global warming to well below two degrees Celsius and pursue efforts to keep it to 1.5 degrees compared to pre-industrial levels.
Romanello called for an integrated approach so that governments stop responding to emergency after emergency. She asked for a cohesive long-term response that builds resilience and capacities so countries can avoid future crises.
Professor Ollie Jay of the University of Sydney explained the methodology. Researchers compiled the number of heat-related deaths recorded by states and subtracted those that would have occurred without climate change. Jay said the intensity and frequency of periods of intense heat were amplified by climate change. He pointed out that last year an extreme drought affected more than half of the world’s land surface for at least one month.
Rising temperatures have also impacted the global economy. By reducing worker productivity, warming has cost more than one trillion dollars per year over the past three years. Southeast Asia and Africa are the hardest-hit regions, losing the equivalent of 3.9 percent and 3.2 percent of their GDP respectively, compared with 0.2 percent for Europe and 1.5 percent for the Americas.
The study found concrete progress in some areas. Since 2016, 56 of the World Health Organization’s 194 member states have adapted their health and early-warning systems to anticipate extreme events. Investment in clean energy reached $2.1 trillion in 2025, which is double the amount invested in fossil fuels.
Fossil fuels still account for 80 percent of global energy. Air pollution from fossil fuels results in 2.73 million deaths per year, though roughly 323,000 deaths have been avoided in at least 77 countries where air pollution has fallen since 2016.
Funding for climate-related medical research increased sevenfold to reach $316 million in 2024. Yet 84 percent of these funds go to researchers in wealthy countries, while the least developed nations are the most affected.
Romanello said researchers faced obstacles this year due to the disappearance of certain data sources, particularly from the United States. US authorities have not made data on fossil fuel subsidies public. She also said global geopolitical instability has pushed global warming and its health impact into the background over the past two years, stressing that inaction makes the situation worse.
