2025 was third hottest year on record as 'human activity' blamed

Last year was globally the third warmest year on record, scientists confirmed as human activity drives the “unmistakable trend” towards a hotter climate.

Scientists around the world, including Ireland, have released their data for 2025, revealing it was the third year in a row with temperatures more than 1.4C above pre-industrial levels.

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Last year was 1.41C above the baseline of 19th century temperatures, behind 2024’s record heat, and 2023, according to the Hadcrut5 dataset collated by the Met Office, UEA and Ncas, while the Europe’s Copernicus Era5 analysis put temperatures at 1.47C above pre-industrial levels.

The Hadcrut5 dataset puts the average temperature over the past three years at 1.47C above 1850 to 1900, while the Copernicus monitoring found they averaged more than 1.5C above pre-industrial levels.

Professor Tim Osborn, director of UEA’s Climate Research Unit, said the previous two years had been made even hotter by a natural climate variation in the Pacific Ocean, the El Nino pattern, which added around 0.1C to global temperatures.

That weakened in 2025 – revealing a clearer picture of underlying, human-driven warming, he said.

“Sharp and sustained reductions in greenhouse gas emissions would slow, and eventually stop, further human-caused changes in the world’s climate,” he said.

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Climate scientist Colin Morice, of the UK Met Office, said: “The long-term increase in global annual average temperature is driven by the human-induced rise in the concentration of greenhouse gases in the atmosphere.

“Fluctuations in the year-to-year temperature largely result from natural variation in the climate system.”

Scientists confirmed the primary driver of global warming is human activity, mostly burning fossil fuels.

With analyses putting long-term temperatures 1.37C and 1.4C above pre-industrial levels, experts warned the world was approaching the 1.5C limit agreed by countries in the Paris climate agreement, to avoid the worst impacts of droughts, floods, extreme heat, wildfires and nature collapse.

The scientists from Copernicus also said the past 11 years were the warmest on record.

Carlo Buontempo, director of the Copernicus Climate Change Service, said: “The fact that the last 11 years were the warmest on record provides further evidence of the unmistakable trend towards a hotter climate.

“The world is rapidly approaching the long-term temperature limit set by the Paris agreement.

“We are bound to pass it; the choice we now have is how to best manage the inevitable overshoot and its consequences on societies and natural systems.”

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Commenting on the findings, Prof Richard Allan, climate scientist at the University of Reading, said: “The sustained warmth into 2025, without the natural warming influence of El Nino, underscores the urgency of halting the heating of planet Earth and growing climate impacts by rapidly cutting greenhouse gases across all sectors of society.”

John Marsham, Professor of Atmospheric Science at the University of Leeds, said: “Impacts on ecosystems, and human food and water systems are  rapidly escalating and we are risking a climate that, in my kids’ lifetimes, is almost as different from our natural climate as the last ice-age was, only hotter instead of colder.

“This will be catastrophic for ecosystems, human health, and our food and water systems.”

He said: “At the recent National Emergency Briefing on Climate and Nature, MPs heard that the UK taking action can be profit making, even if other countries don’t act – with renewables lowering costs, creating jobs and providing energy security,” adding people needed to call for urgent action.