UN says greenhouse gas levels hit new records in 2025, locking in long-term warming

Record concentrations in 2025

On Tuesday, 27 October 2026, the World Meteorological Organization (WMO) published its 22nd annual Greenhouse Gas Bulletin, which says the three main greenhouse gases all reached unprecedented levels in 2025. The bulletin tracks how much of each gas is in the atmosphere, not how much is emitted in a given year. Carbon dioxide stood at 426.8 parts per million, methane at 1,948 parts per billion and nitrous oxide at 339.1 parts per billion. Those readings equal 153%, 267% and 126% of pre-industrial levels from before 1750. Carbon dioxide accounts for about 66% of the warming effect of the three gases.

Carbon dioxide153%

Methane267%

Nitrous oxide126%

Carbon dioxide

153 %

Methane

267 %

Nitrous oxide

126 %

Data from the article text

A smaller rise in carbon dioxide

The global average CO2 concentration rose by 2.8 ppm from 2024 to 2025, less than the surge of 3.6 ppm recorded from 2023 to 2024. WMO senior scientific officer Oksana Tarasova linked the slowdown to the recovery of land carbon sinks and lower fire emissions in 2025, following the strong 2023/2024 El Niño. Around half of the CO2 emitted each year stays in the atmosphere, while land and oceans absorb the rest. The 2.8 ppm increase is still above the average growth rate of 2.6 ppm for the past decade, which stood at 0.8 ppm in the 1960s. Tarasova put the concern plainly.

2023 to 20243.6

2024 to 20252.8

2023 to 2024

3.6 ppm

2024 to 2025

2.8 ppm

Data from the article text

“However, a 2.8 ppm annual increase is still a substantial addition of carbon to the atmosphere from fossil fuel burning.”

Warming that outlasts emissions

The bulletin says the higher concentrations lock in climate impacts that will persist for centuries, and that the rise would lead to further long-term temperature increases for the planet. WMO deputy secretary-general Ko Barrett said greenhouse gases are trapping an unprecedented amount of heat in the atmosphere.

“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.”

Barrett added that the past 11 years have been the warmest on record and that carbon dioxide will affect the global climate for decades and even centuries. The figures arrive ahead of COP31, the UN climate summit running from 9 to 20 November in Antalya, Turkey. The bulletin adds to the debate that the summit will take up.