WMO: CO₂ reaches 426.8 ppm, all three main greenhouse gases at record highs

Average atmospheric carbon dioxide reached 426.8 parts per million (ppm) in 2025, the World Meteorological Organization (WMO) said on October 27 in its annual Greenhouse Gas Bulletin. That is 153 percent of the 1750 level.

The rise from 2024 was 2.8 ppm, above the average of the past decade but slightly below the 2023/24 jump. Methane reached 1,948 parts per billion (267 percent of the pre-industrial level) and nitrous oxide 339.1 (126 percent). All three gases, along with sulphur hexafluoride, are at record levels.

Every part counts

"Every additional part per million matters because it traps additional heat," said WMO Deputy Secretary-General Ko Barrett. CO₂ stays in the atmosphere for centuries, so today's concentrations set temperatures for future generations too.