The climate crisis caused an additional six weeks of dangerously hot days for the average person in 2024, significantly amplifying the lethal effects of heatwaves globally.

The impact of human-induced global heating was particularly severe for those in Caribbean and Pacific island nations, where many endured nearly 150 extra days of dangerous heat—almost half the year—compared to a world without global warming, accroding to an analysis by World Weather Attribution (WWA) and Climate Central.

Nearly half of the world’s countries experienced at least two months of elevated temperatures. Even in less affected regions, such as the UK, US, and Australia, carbon pollution from burning fossil fuels led to an additional three weeks of dangerous heat.

Heatwaves, the deadliest consequence of the climate emergency, have underscored the urgent need to phase out coal, oil, and gas to prevent further escalation. Scientists predict 2024 will be the hottest year on record, driven by unprecedented carbon emissions.

The lack of real-time reporting of heatwave-related deaths means the current data significantly underestimates the human toll. Researchers estimate that uncounted millions may have already died from the impacts of global heating over recent decades. Enhanced monitoring is critical to understanding and addressing this escalating crisis.

“The impacts of fossil fuel warming have never been clearer or more devastating than in 2024 and caused unrelenting suffering,” said Dr Friederike Otto, of Imperial College London and the co-lead of WWA. “The floods in Spain, hurricanes in the US, drought in the Amazon, and floods across Africa are just a few examples. We know exactly what we need to do to stop things from getting worse: stop burning fossil fuels.”

The analysis, conducted by World Weather Attribution (WWA) and Climate Central, identified “dangerous heat days” based on local thresholds for the hottest 10% of days from 1991 to 2020. These thresholds correlate with heightened health risks. By comparing the number of dangerous heat days in 2024 with a scenario without global warming, researchers calculated that the average person experienced 41 additional hot days this year due to the climate crisis.

In Indonesia, home to 280 million people, residents endured 122 extra dangerous heat days, a burden shared by Singapore and many Central American nations. In the Middle East, Saudi Arabia faced 70 additional hot days, during a year when extreme heat contributed to the deaths of at least 1,300 hajj pilgrims. Brazil and Bangladesh experienced about 50 extra hot days, while Spain, Norway, and Balkan countries saw an additional month of extreme temperatures.

On 21 July, one of the year’s hottest days, five billion people—nearly two-thirds of the global population—experienced temperatures made at least twice as likely by global heating.

Hurricanes were also supercharged by the climate crisis in 2024. Kristina Dahl, the vice-president for science at Climate Central, said: “Our analyses have shown that every Atlantic hurricane this year was made stronger by climate change, and that hurricanes Beryl and Milton, which were both category five storms, would not have reached that level were it not for climate change.”

Recent analysis by WWA also linked an extraordinary sequence of six typhoons in the Philippines within 30 days, which affected 13 million people, to the intensifying climate crisis.

Julie Arrighi, the programmes director at the Red Cross Red Crescent Climate Centre, said: “Another devastating year of extreme weather has shown that we are not well prepared for life at [the current level] of warming. In 2025, it’s crucial that every country accelerates efforts to adapt to climate change and that funds are provided by rich nations to help developing countries become more resilient.”

To mitigate these impacts, researchers emphasise the need for better early warning systems and improved reporting of heat-related deaths, both of which have proven effective in saving lives.

“In most countries there is no reporting on heatwaves at all, which means the numbers we have are always a very gross underestimate,” Otto said. “If we can’t communicate convincingly that actually lots of people are dying, it’s much harder to raise awareness that heatwaves are by far the deadliest extreme events, and they are the extreme events where climate change is a real gamechanger.”