Greenhouse gas levels once again reach record high

Geneva, Switzerland (WMO) – Levels of carbon dioxide (CO₂) and other major greenhouse gases in the atmosphere reached unprecedented highs in 2025, locking in more long-term temperature increase for the planet, according to a new report from the World Meteorological Organization (WMO).

The WMO Greenhouse Gas Bulletin reported that the globally averaged surface concentration of CO₂ in 2025 was 426.8 parts per million, or 153% of the 1750 pre-industrial baseline. Concentrations of methane and nitrous oxide - the second and third most important long-lived greenhouse gases related to human activities - also rose to a new record.

“Another year, another new record. Greenhouse gases are trapping an unprecedented amount of heat in the atmosphere, providing energy for more extreme weather and associated risks to our economies and societies.  The past 11 years have been the warmest on record and this trend is set to continue. CO₂ has a very long life-time and so will affect the global climate not just for years but for decades and even centuries,” said WMO Deputy Secretary-General Ko Barrett.

WMO releases the Bulletin, one of its flagship annual publications, to provide authoritative scientific information for negotiators at the UN Climate conference. The COP 31 meeting in Antalya, Türkiye, from 9-20 November 2026 is seeking to turn climate commitments into concrete actions.