Global warming has hit “a milestone” as average temperatures have exceeded the critical 1.5C threshold for the longest period yet, European scientists warned on Wednesday.

According to the EU’s Earth observation service Copernicus, 2025 ranks as the third-warmest year on record, behind 2023 and 2024, with global temperatures averaging more than the Paris Agreement’s most ambitious limit for the first time over a three-year period.

“Exceeding a three-year average of 1.5C above pre-industrial levels is a milestone none of us wished to reach,” said Mauro Facchini, head of the Unit for Earth Observation in the European Commission.

Samantha Burgess, deputy director at Copernicus, said the last three years had been “exceptionally warm” as a result of the record amount of greenhouse gases in the atmosphere, primarily caused by burning fossil fuels, as well as record ocean heat, fuelled in part by the El Niño weather pattern.

“New era of climate extremes” as global warming fuels devastating impacts in 2025

In 2025, global temperatures were 1.47 degrees Celsius above pre-industrial levels, slightly cooler than in 2023 and 0.13C lower than in 2024, the hottest year on record, according to the Copernicus analysis.

Temperatures in tropical regions in 2025 were lower than in 2023 and 2024, influenced by a weak La Niña, which is when surface waters in the Pacific Ocean are cooler than usual.

Paris pact’s 1.5C goal to be breached this decade

When governments adopted the 2015 Paris Agreement, they committed to holding the increase in the global average temperature to “well below 2C above pre-industrial levels” and pursuing efforts to limit the temperature increase to 1.5C.

Scientists with the Intergovernmental Panel on Climate Change and the World Meteorological Organisation say that temperature increases should be measured over 20-year periods, meaning that a one-year or a three-year breach does not mean the Paris targets have been missed.

But the European agency expects that, based on the current rate of warming, the world will reach the threshold of long-term warming above 1.5C before the end of 2029, over a decade earlier than scientists had predicted at the time the Paris accord was signed.

“The expectation was that emissions would be reduced more rapidly than what we’ve observed over the last decade,” said Burgess. “That’s really the big difference between where we thought the world would look back in 2015, versus where it looks now at the beginning of 2026.”

For the first time last year, United Nations Secretary-General António Guterres conceded that a “temporary overshoot” of the 1.5C warming threshold was inevitable, starting in the early 2030s at the latest. He told global leaders gathered at the COP30 summit in November that failure to curb global heating amounted to “moral failure and deadly negligence”.

Commenting on the Copernicus findings, Helen Clarkson, CEO of the US-based Climate Group, which builds networks working for net-zero emissions, said the average of 1.5C of warming over the past three years showed “the warnings of scientists are becoming a dangerous reality”. Governments that do not act to cut emissions are putting their economic security at risk, she emphasised.

“Too many leaders are propping up fossil fuels, blocking people and businesses from accessing the cost savings and benefits of cheap, clean energy. But we can break this trend: accelerate the transition to renewables, electric cars and clean electrification,” she added.

Antarctic saw hottest year on record

Scientists have warned that, while the temperature limit is not a cliff edge, every additional fraction of a degree of warming increases the frequency and intensity of extreme weather events such as heatwaves, droughts and storms, triggering severe impacts.

In 2025, polar regions experienced significant temperature anomalies, with the Antarctic seeing its hottest year on record and the Arctic its second-warmest, the Copernicus analysis found. That partly offset the less extreme temperatures observed in tropical regions last year.

Global warming is causing the world’s ice caps to melt at an accelerating pace. In February 2025, the combined sea ice cover from both poles fell to its lowest value since at least the start of satellite observations in the late 1970s, the EU agency said.

Burgess expects that 2026 will be among the top five warmest years, with temperatures comparable to 2025, but she noted it is too early to tell how natural climate cycles will develop over the coming months and affect human-made global warming.

The longer-term trend, however, is for continued rises in temperatures, she said.

“When we look at the continued rate of emissions from countries around the world, the reality is, unfortunately, that the last three years we have experienced – when we look back in five years’ time – will be cooler than average rather than continue to be exceptional,” she told journalists.

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Global warming topped key 1.5C limit over last three years, EU scientists say