Heat Deaths Up Nearly 36% as Climate Harms to Health Accelerate, Report Finds

October 28 — A major global assessment published on Wednesday shows that climate change’s negative effects on human health are not only worsening but worsening faster than they were a decade ago.

The report is the tenth annual edition from the Lancet Countdown, an international collaboration of scientists that tracks the relationship between global warming and human health. This edition compares the two decades before and after the Paris Agreement was signed and finds that several major health threats, including deadly heat and drought, have accelerated since. At the same time, countries are stepping up clean energy investment and taking measures to protect people from climate disasters.

The report comes after Europe endured a summer of savage heat, with heatwaves causing tens of thousands of deaths, and shortly before the UN holds its COP31 climate summit in Turkey.

The analysis finds that from 2016 to 2023 the annual number of heat-related deaths worldwide was almost 36% higher than in 2006 to 2015. In 2023 alone, heat was linked to about 710,000 deaths globally. Heat exposure is also dragging on GDP, with South-East Asia and Africa hit hardest.

The Lancet Countdown has for the first time calculated heat-related deaths attributable to human-caused climate change. Researchers estimate that more than 70% of heat-related deaths in 2023 can be attributed to global warming, and that the cumulative figure for 2016 to 2023 approaches 3 million.

Beyond heat, water-related risks are also rising. In 2025, nearly 52% of the world’s land experienced at least one month of extreme drought — the second-highest level on record.

A satellite analysis found that since 2003 about 80% of the world’s land has shown a long-term trend of either wetting or drying. Such shifts could threaten crop production, drinking water supplies and the operation of sanitation. The current El Niño is expected to worsen drought in some regions, with effects possibly lasting into next year.

Simon Stiell, executive secretary of the UN Framework Convention on Climate Change, said in a statement: “The climate crisis is having extremely devastating effects on human health.” He noted that the impacts span many areas, from “deadly heatwaves and floods to food insecurity, pollution and more disease.”

The report was written by 146 researchers from dozens of institutions, tracking 54 indicators to assess the health impacts of climate change and the response to them. Its authors call on governments to put health at the centre of climate and energy policy.

The report also notes that climate action is already delivering health benefits. In at least 77 countries where fossil-fuel-related air pollution has fallen since 2016, cleaner air now avoids about 323,000 deaths a year.

Yet fossil fuels still supply more than 80% of global energy, and air pollution linked to them is estimated to cause 2.7 million deaths a year.

Health systems’ preparedness is improving too. Of the World Health Organization’s 194 member states, 56 now have health adaptation plans for climate change, up from just 14 in 2015.

Emily Bancroft, chief executive of Health Care Without Harm, which works to reduce the health sector’s environmental footprint, said that for many countries finding the money to implement these plans remains a major challenge. “The growing discussion and exchange around this work is genuinely encouraging,” she said. “But to actually deliver, there is still a clear gap in funding.”