GENEVA — Atmospheric concentrations of carbon dioxide, methane, and nitrous oxide climbed to unprecedented highs in 2025, locking in long-term global climate impacts that will persist for centuries, the United Nations announced on Tuesday, Oct. 27, 2026. The 22nd annual Greenhouse Gas Bulletin, published by the World Meteorological Organization, reveals that these trapped gases are providing sustained energy for extreme weather events and mounting economic and societal risks worldwide, according to reporting published by CBS News.
Coming just weeks before the COP31 U.N. climate summit scheduled in Antalya, Turkey, from Nov. 9 to Nov. 20, the WMO findings arrive alongside a separate U.N. evaluation showing that current national climate pledges will cut global greenhouse gas emissions by just 6% by 2035. Scientists emphasize that this reduction falls drastically short of the roughly 60% drop needed to limit global warming to 1.5 degrees Celsius.
Concentration Breakdown Across Major Gases
Unlike annual emissions tracking the burning of coal, oil, and gas, the WMO bulletin measures the cumulative concentration of gases residing in the atmosphere. In 2025, carbon dioxide concentrations reached 426.8 parts per million, methane stood at 1,948 parts per billion, and nitrous oxide registered at 339.1 parts per billion. These figures represent 153%, 267%, and 126% of pre-industrial levels recorded prior to 1750.
Carbon dioxide remains the primary driver, accounting for roughly 66% of the warming effect from long-lived greenhouse gases. Approximately half of annual CO2 emissions remain trapped in the atmosphere, while the remainder is absorbed by land and ocean sinks. From 2024 to 2025, global average CO2 concentration rose by 2.8 parts per million. While smaller than the record 3.6 parts per million surge seen from 2023 to 2024, WMO senior scientific officer Oksana Tarasova noted that the increase remains well above the past decade’s average growth rate of 2.6 parts per million.
Tarasova explained that the slightly reduced annual surge reflects the recovery of land carbon sinks and lower fire carbon emissions in 2025, following the strong 2023–2024 El Niño cycle. However, experts warn that concentrations will likely rise further in 2026 due to ongoing fossil fuel combustion and the emergence of a powerful new El Niño phase that will disrupt natural carbon absorption.
Methane Dynamics and Emerging Trace Gases
Methane accounts for approximately 16% of long-lived warming impacts. Roughly one-third of atmospheric methane originates from natural sources like wetlands, while anthropogenic contributions stem from livestock, rice farming, landfills, and biomass burning. Beyond primary gases, the WMO urged greater international scrutiny of two trace gases closely tied to electrical infrastructure: molecular hydrogen and sulfur hexafluoride.
Sulfur hexafluoride has increased steadily over three decades due to its use as a spark suppressant in electricity distribution. Meanwhile, molecular hydrogen levels have risen over the past decade amid its growing adoption as an energy storage medium, though exact drivers behind its atmospheric accumulation remain under study.
The COP31 Policy Gap and Financial Realities
The alarming bulletin coincides with a broader U.N. synthesis report covering national climate submissions from 154 countries, which together account for 71% of global emissions. The analysis demonstrates that even if nations fully implement their current intended contributions and meet conditional targets, overall emissions reductions by 2035 will reach only 9%.
This policy deficit is further compounded by the geopolitical backdrop, including the United States’ withdrawal from the Paris Agreement under President Donald Trump. U.N. climate chief Simon Stiell emphasized that the upcoming COP31 negotiations in Turkey must bridge these implementation gaps through practical support measures. While global climate finance flows grew by 32% to reach an average of $1.9 trillion annually in 2023 and 2024, institutional reports confirm that current financial mobilization still lags far behind what is required to alter the global emissions trajectory.