The threats from climate change, such as more intense heat waves and rising sea levels, increase with every tenth of a degree of warming. Scientists also warn that passing 1.5C risks triggering so-called tipping points, from rainforest diebacks to ocean circulation collapse, that bring about irreversible and extreme climatic changes.
In theory, the world could return to 1.5C after crossing it by using technology to remove vast amounts of carbon dioxide from the atmosphere, a scenario known as “overshoot.” This technology, however, is not yet available at the scale required.
“With the 1.5C in the terms of the Paris Agreement around the corner, now we are effectively entering a phase where it will be about managing that overshoot,” Carlo Buontempo, director of the Copernicus Climate Change Service, told reporters at a press conference.
“It’s basically inevitable that we will pass that threshold, and it’s up to us to decide how we want to deal with the enhanced and increased higher risk that we will face as a consequence of this,” he said. The longer and greater the overshoot, the bigger the risk, he added.
The hottest year — and the only one so far to exceed the 1.5C threshold — remains 2024 with 1.6C. However, the Paris Agreement targets refer to long-term trends rather than those lasting a few years, and Buontempo said three different Copernicus models, including five-year averages and 30-year linear trends, showed warming has now reached around 1.4C.
Copernicus data shows that 2025 was the third-warmest year on record at 1.47C above pre-industrial levels, just marginally cooler than 2023. That’s despite El Niño, a naturally occurring climate pattern that tends to bring hotter temperatures on top of the human-induced warming, ending in mid-2024 and a cooling La Niña phase emerging late last year.