Greenhouse gas levels hit record highs in 2025, driving further global warming: WMO

Greenhouse gas levels hit record highs in 2025, driving further global warming: WMO

Atmospheric CO2 concentrations reach 426.8 parts per million, while methane and nitrous oxide also set new records ahead of COP31 UN Climate Change Summit hosted by Türkiye

Beyza Binnur Dönmez

27 October 2026•Update: 27 October 2026

CENEVRE

Concentrations of carbon dioxide (CO2), methane, and nitrous oxide in the atmosphere reached record highs in 2025, committing the planet to further warming for decades and centuries to come, the World Meteorological Organization (WMO) warned Monday.

In its latest Greenhouse Gas Bulletin, the UN weather agency said globally averaged CO2 concentrations reached 426.8 parts per million, equivalent to 153% of pre-industrial levels seen in 1750, the baseline year.

"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," said Ko Barrett, the WMO’s deputy secretary-general.

She warned that the past 11 years had been "the warmest on record" and that the warming trend is expected 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," she said.

The report found that annual CO2 growth rates have tripled since the 1960s, rising from 0.8 to 2.4 parts per million annually during 2011-2020.

Between 2024 and 2025, concentrations rose by another 2.8 parts per million, driven partly by continued fossil fuel combustion.

Methane concentrations reached 1,948 parts per billion, or 267% of pre-industrial levels, while nitrous oxide climbed to 339.1 parts per billion, equivalent to 126% of the baseline from 1750.

The WMO also warned that sulfur hexafluoride, widely used in electricity distribution, saw its largest annual increase in 2025 despite having a warming potential approximately over 24,000 times greater than CO2.

The findings come on the eve of the COP31 UN Climate Change Conference hosted by Türkiye, set to start on Nov. 9, where governments are expected to discuss translating climate commitments into concrete action.