Washington: Half of the world’s population has endured an additional month of extreme heat in the past year due to artificial climate change, found a new study.
The results underline how the continuous burn of fossil fuels affects health and well-being on all continents, the effects particularly recognized in developing countries, the authors said.
“With each barrel of burned oil, each tonne of freed carbon dioxide and each fraction of a degree of warming, heat waves will affect more people,” said Friederike Otto, climatologist at Imperial College in London and co-author of the report.
The analysis – conducted by scientists from World Weather award, Central Climate and the Red Cross Red Cross Cross Climate – was published before the World Day of Heat Action on June 2, which is putting this year to the dangers of heat and heat stroke.
To assess the influence of global warming, the researchers analyzed the period from May 1, 2024 to May 1, 2025.
They defined “extreme heat days” like those warmer than 90% of the temperatures recorded in a given location between 1991 and 2020.
Using a modeling approach evaluated by peers, they then compared the number of these days to a simulated world without warming caused by humans.
The results were marked: around four billion people – 49% of the world’s population – experienced at least 30 days of extreme heat more than they would have otherwise.
The team identified 67 extreme heat events during the year and found the fingerprint of climate change on each of them.
The Caribbean island of Aruba was the least affected, recording 187 days of extreme heat – 45 more than expected in a world without climate change.
The study follows one year of unprecedented global temperatures. 2024 was the hottest year ever recorded, exceeding 2023, while January 2025 marked the hottest January of all time.
Over an average at five years, global temperatures are now 1.3 degrees Celsius above pre-industrial levels-and in 2024 only, they exceeded 1.5 ° C, the symbolic ceiling established by the Paris climate agreement.
The report also highlights a critical lack of data on the health impacts related to heat in low -income regions.
While Europe has recorded more than 61,000 heat-related deaths in the summer of 2022, comparable figures are rare elsewhere, with many deaths related to heat poorly attributed to underlying conditions such as heart or pulmonary diseases.
The authors highlighted the need for early alert systems, public education and heat action plans adapted to cities.
Better design of the building – including shade and ventilation – and behavioral adjustments such as avoiding intense activity during maximum heat are also essential.
However, adaptation alone will not be enough. The only way to stop the gravity and the frequency of extreme heat, have warned the authors, is to quickly remove fossil fuels.
