Greenhouse gas concentrations hit record highs in 2025, WMO reports
WMO’s new bulletin records highs for carbon dioxide, methane and nitrous oxide in 2025, and explains why slower annual growth does not mean falling levels
GENEVA — Carbon dioxide, methane and nitrous oxide reached record global atmospheric concentrations in 2025, according to a new report from the World Meteorological Organization (WMO), highlighting the continuing build-up of the gases that drive global warming.
The WMO’s Greenhouse Gas Bulletin No. 22, released on Tuesday, October 27, found that the global average concentration of carbon dioxide (CO₂) reached 426.8 parts per million (ppm). Methane reached 1,948 parts per billion (ppb) and nitrous oxide 339.1 ppb.
The three gases stood 53%, 167% and 26% above pre-industrial (1750) levels, respectively.
“Greenhouse gases are trapping an unprecedented amount of heat in the atmosphere,” WMO Deputy Secretary-General Ko Barrett said.
What the figures measure
The bulletin tracks concentrations, meaning how much of each gas has accumulated in the atmosphere, rather than annual emissions. About half of the carbon dioxide emitted each year remains in the atmosphere, while land ecosystems and oceans absorb most of the rest.
Carbon dioxide concentrations rose by 2.8 ppm between 2024 and 2025. That increase was smaller than the unusually large rise between 2023 and 2024 but slightly above the average annual increase of the past decade. A slower increase still adds to the total: the amount of carbon dioxide in the atmosphere continues to grow.
Why the findings matter
Carbon dioxide remains in the climate system for long periods, so the gases already accumulated will influence global temperatures for decades and even centuries.
The findings are based on observations from the WMO’s Global Atmosphere Watch network. The report comes ahead of the UN COP31 climate conference, scheduled for November 9–20 in Antalya, Türkiye.
