Greenhouse Gases in the Air Reached New Highs in 2025, WMO Reports
The World Meteorological Organization published the 22nd edition of its annual Greenhouse Gas Bulletin on Oct. 27, 2026, reporting that globally averaged surface concentrations of the three main long-lived greenhouse gases all reached record levels in 2025. The figures are carbon dioxide at 426.8 parts per million, methane at 1,948 parts per billion and nitrous oxide at 339.1 parts per billion, drawn from the WMO Global Atmosphere Watch network of ground-based measuring stations.
WMO says it publishes the bulletin to give negotiators at the UN climate conference authoritative scientific information; the meeting, COP31, runs in Antalya, Türkiye, in November 2026. The numbers are concentrations, meaning how much of each gas is in the air, rather than emissions, so they track what has built up over time and not what was released in a single year.
WMO puts carbon dioxide 53% above pre-industrial levels, methane 167% above and nitrous oxide 26% above. It describes carbon dioxide's increase from 2024 to 2025 as lower than the unusually large increase of the year before, but slightly higher than the average annual growth rate of the past decade. Methane's increase was lower on both of those comparisons, and nitrous oxide's was the same as the previous year's and close to the decade average.
"Another year, another new record," said WMO Deputy Secretary-General Ko Barrett in the organization's news release. "The past 11 years have been the warmest on record and this trend is set to continue."
