The three main greenhouse gases reached unprecedented concentrations globally in 2025, continuing an upward trend that will lead to more global warming, the World Meteorological Organization (WMO) warns.
The WMO Global Atmosphere Watch programme has published its annual bulletin on the amount of greenhouse gases that have accumulated in the atmosphere, ahead of the UN’s COP31 climate conference, which will be held in Turkey in November.
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It reports that the global average surface concentration of carbon dioxide reached a record 426.8 parts per million (ppm) in 2025, which is 53 per cent higher than pre-industrial levels.
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The increase from 2024 to 2025 was slightly higher than the average annual growth rate over the past decade, but the increase wasn’t as steep as the previous year.
The levels of methane and nitrous oxide also reached record highs of 1948 parts per billion (ppb) and 339.1 ppb respectively in 2025, an increase of 167 per cent and 26 cent on pre-industrial levels.
“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,” WMO Deputy Secretary-General Ko Barrett said in a statement.
This follows the UN recently confirming that the global target to limit warming to 1.5°C above pre-industrial levels is due to be exceeded in the next few years, with emissions on track to cause 2.8°C of warming by the end of the century.
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The WMO report also warns that more attention should be given to the steadily rising levels of two other gases in the atmosphere, molecular hydrogen and sulphur hexafluoride, as more countries decarbonise their energy systems.
Although hydrogen isn’t a greenhouse gas, it has a strong indirect effect on global warming and is being used for energy storage. Its concentration increased by 5.3 per cent between 2010 and 2024.
Sulphur hexafluoride, used primarily as a spark suppressant in electricity distribution, has the highest 100-year global warming potential overall – approximately 24,000 times that of CO2. According to the WMO, levels have been increasing steadily over the past three decades in proportion to growing global electrification.