This article has been reviewed according to Science X's editorial process and policies. Editors have highlighted the following attributes while ensuring the content's credibility: Greenhouse gas concentrations in the atmosphere rose to new record highs in 2025, locking in climate impacts that will persist for centuries to come, the United Nations said Tuesday. Levels of the three main greenhouse gases—the climate-warming carbon dioxide, methane and nitrous oxide—all rose to unprecedented figures in 2025, the U.N.'s weather and climate agency said.
The World Meteorological Organization said the rise would lead to more long-term temperature increases for the planet. The WMO's 22nd annual Greenhouse Gas Bulletin comes ahead of the COP31 U.N. climate summit in Antalya, Turkey, running from Nov. 9 to 20. "Another year, another new record," said WMO Deputy Secretary-General Ko Barrett.
"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. Carbon dioxide (CO₂) has a very long lifetime and so will affect the global climate not just for years but for decades and even centuries." The bulletin looks at greenhouse gas concentrations—the amount of those gases in the atmosphere—rather than new annual emissions amounts as the world burns more coal, oil and gas.
In 2025, carbon dioxide concentrations were at 426.8 parts per million (ppm), methane at 1,948 parts per billion, and nitrous oxide at 339.1 parts per billion. That takes them respectively to 153%, 267% and 126% of the preindustrial levels witnessed before 1750. Of the three major greenhouse gases, CO₂ accounts for about 66% of the warming effect on the climate.
Around half of the total CO₂ emitted each year remains in the atmosphere; the rest is absorbed by the land and oceans. From 2024 to 2025, the global average concentration of CO₂ rose by 2.8 ppm—smaller than the record surge from 2023 to 2024 of 3.6 ppm. WMO senior scientific officer Oksana Tarasova said this reflected the "recovery of the land carbon sinks and reduced fire carbon emissions in 2025 after the strong 2023/2024 El Niño," the naturally occurring, climate-warming weather phenomenon.
"However, a 2.8 ppm annual increase is still a substantial addition of carbon to the atmosphere from fossil fuel burning." It is also above the average growth rate over the past decade of 2.6 ppm—a figure that stood at 0.8 ppm in the 1960s. Monitoring station data show that CO₂ levels have continued rising in 2026. "Every additional part per million matters because it traps additional heat," Barrett told reporters.
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