The Lancet has published a report urging governments to declare climate change a global health emergency, and it arrives just weeks before the COP-31 climate summit in November. The researchers say the step is needed before health protection can take real priority in government policy.

The numbers are grim. Between 2016 and 2023, extreme heat killed roughly 3 million people worldwide. In 2023 alone, heat was linked to a record 710,000 deaths, and the researchers estimate that more than 70 percent of those deaths were caused by climate change driven by human activity.

The study was carried out by 146 researchers from 30 countries, who examined how climate change is affecting human health across the globe. The report was published by the British medical journal ahead of the November summit, putting the health cost of warming directly into the global climate conversation.

Three million heat deaths in eight years

The headline figure is hard to ignore. Since the 2015 Paris Agreement, the researchers recorded about three million heat-related deaths over eight years. They estimate that 68 percent of them were caused by climate change.

To work out how many deaths came from human-caused warming, the team looked at heat-related deaths recorded in different countries. They then removed the deaths that would have happened even without climate change. What remains is a picture of people dying because the planet has already warmed.

A researcher from the University of Sydney explained that climate change is making high temperatures more intense and more frequent. That shift is what turns a hot summer into a deadly one for the elderly, the sick, and outdoor workers who have no shade and no way out.

The report also found that more than half of the world’s land area experienced at least one month of severe drought last year. Drought and heat often arrive together, and the combination puts pressure on food, water, and health systems at the same time.

Why the researchers want long-term planning

The researchers are pushing governments to stop reacting to each crisis as it hits. Their argument is that the health emergencies caused by climate change will keep coming, and that only long-term planning can keep pace with them.

Governments cannot keep responding to each heat wave as if it were a one-off. The health threat is now a permanent feature of the climate, and planning has to match that reality.

The warning is that the health sector is still being treated as an afterthought in climate policy. Without a formal emergency declaration, the researchers argue, health protection is unlikely to move up the list of government priorities.

The economic bill is climbing

Heat is also hitting wallets. According to the researchers, rising temperatures have reduced workers’ productivity, and the global economy has lost more than $1 trillion a year over the past three years.

The losses are uneven. Southeast Asian countries lost 3.9 percent of their gross domestic product, while Africa lost 3.2 percent. The Americas lost 1.5 percent, and Europe lost 0.2 percent. The countries that can least afford these hits are often the ones taking the biggest damage.

That pattern runs through the entire report. The researchers note that poorer countries face the greatest climate-related health threats, yet they receive a small share of the money meant to study those threats.

Early warnings and clean energy

There is some progress in the data. Since 2016, 56 of the 194 member states of the World Health Organization have improved their health early warning systems, which are designed to flag severe weather before it turns into a health disaster.

Investment in clean energy is also rising fast. In 2025, global investment in clean energy reached $2.1 trillion, double the amount spent on fossil fuels.

But the transition is far from finished. Fossil fuels still supply about 80 percent of the world’s energy needs. The air pollution they produce is linked to 2.73 million deaths every year.

There is some good news in that figure too. Since 2016, at least 77 countries have reduced fossil fuel pollution, which the researchers estimate prevented around 323,000 deaths. The findings suggest that cleaner air saves lives within a relatively short window, but only where governments act.

Funding gap and missing data

Research money is growing, but it is not reaching everyone. Funding for studies on climate change and health rose to $316 million in 2024. However, 84 percent of that money went to researchers in wealthy countries.

The researchers also warned that some countries, including the United States, have not provided the data needed for their work. That gap makes it harder to measure the true toll of heat and pollution, especially in the regions hit hardest.

Political instability has added another layer. The researchers warned that over the past two years, global attention on climate change and its health impacts has declined because of international political tensions. They say that neglect is making the situation worse.

The message from the report is direct. Heat is already killing people on a large scale, the economic damage is mounting, and the countries least responsible for the crisis are carrying the heaviest burden. Whether the COP-31 summit responds with real action will determine how many more lives are lost in the years ahead.