2025 among the hottest years | “A milestone that no one wanted to cross”

1,47 °C

As expected, 2025 ranks as the third warmest year on record, with an average temperature 1.47°C above the level observed at the start of the pre-industrial era. More and more scientists are now convinced that it will be virtually impossible to limit global warming to 1.5°C, as set out in the Paris Agreement adopted in 2015. Limiting warming to 2°C is not out of reach, but this target is increasingly unrealistic unless nations rapidly reduce their greenhouse gas (GHG) emissions.

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Global temperatures over the past three years (2023-2025) have been on average more than 1.5°C higher than pre-industrial levels. This is the first time that a period of three years has exceeded the limit of 1.5°C, specifies the Copernicus agency, which unveiled its most recent report on Tuesday on the highlights of the global climate. During the same period, CO emissions₂ of fossil origin continued to increase, reaching a record level of 38.1 billion tonnes in 2025. “Exceeding a three-year average of 1.5°C above pre-industrial levels is a milestone that no one wanted to achieve, but it reinforces the importance of Europe’s leading role in climate monitoring to inform both mitigation and adaptation,” said Mauro Facchini, head of Earth observation at the European Commission.

1,5 °C

Since 1850, the planet has warmed by 1.4°C, reports Copernicus. At the current rate, the 1.5°C barrier would be crossed by the end of the decade, estimate experts from the European agency. “The fact that the last 11 years have been the warmest on record provides further evidence of the undeniable trend towards a warmer climate,” says Carlo Buontempo, director of climate services at Copernicus. If the trend continues, the planet will warm by around 2.9°C by the end of the century, climatologists estimate.

426,5

In 2025, the concentration of CO₂ in the atmosphere stood at 426.5 parts per million (ppm). This data represents the ultimate unit of measurement of our efforts to reduce our polluting emissions. However, this value has increased by 50% since around 1750, when it was 280 ppm. Although it represents only 0.04% of the composition of the atmosphere, carbon dioxide retains heat, unlike nitrogen or oxygen, two molecules which do not cause the famous greenhouse effect. If the trend continues, the CO concentration₂ in the atmosphere would reach more than 600 ppm by the end of the century. At such a level, the consequences for the oceans would be major: they would be much more acidic and the oxygen concentration would be even lower.

15 %

Global warming is increasingly affecting natural sources of carbon, such as forests and oceans. We learned over the last year that part of the Amazon forest and part of the Australian forest, among others, now release more CO₂ than they absorb any. A study published in the journal Nature in 2025 also reports that the absorption capacity of marine and terrestrial carbon sinks in a warmer climate has decreased by 15% over the last decade. Basically, we are emitting more and more carbon and the natural capacity of ecosystems to absorb it is diminished.