The World Meteorological Organization (WMO) reported that atmospheric concentrations of the major long-lived greenhouse gases reached new record highs in 2025.
According to the WMO Greenhouse Gas Bulletin No. 22 (released around 27 October 2026), the globally averaged surface concentration of carbon dioxide (CO₂) in 2025 was 426.8 parts per million (ppm). This is about 153% of the 1750 pre- industrial level (a roughly 53% increase). Methane (CH₄) and nitrous oxide (N₂O) also hit new records.
Key figures for 2025
- CO₂: 426.8 ppm (up 2.8 ppm from 2024). This annual rise was above the recent decadal average but lower than the exceptional jump in 2023- 2024. Growth rates of CO₂ have roughly tripled since the 1960s (from ~0.8 ppm/year to ~2.4 ppm/year in 2011- 2020).
- Methane: 1,948 parts per billion (ppb), or 267% of the 1750 level.
- Nitrous oxide: 339.1 ppb, or 126% of the 1750 level.
WMO Deputy Secretary-General Ko Barrett stated: “Another year, another new record. 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. 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 tracks concentrations (the amount accumulated in the atmosphere), not annual emissions. Roughly half of emitted CO₂ stays in the atmosphere; the rest is absorbed by land ecosystems and oceans. The somewhat slower 2024-2025 CO₂ rise is linked to recovery of land carbon sinks and fewer fire emissions after the strong 2023/2024 El Niño. A powerful El Niño developing in 2026 is expected to drive another surge in concentrations, alongside ongoing fossil fuel emissions.
Radiative forcing (the warming effect) from long-lived greenhouse gases rose about 56% from 1990 to 2025, with CO₂ responsible for roughly 81% of that increase (per the NOAA Annual Greenhouse Gas Index).
The report also flags concerns about sulphur hexafluoride (SF₆, used in electrical equipment), which saw a record increase in 2025. It has an atmospheric lifetime of over 1,000 years and a global warming potential roughly 24,300 times that of CO₂. Hydrogen (H₂) levels have also risen and can have indirect warming effects.
The findings are intended to inform discussions at COP 31 (Antalya, Türkiye, 9- 20 November 2026). The data come from the WMO Global Atmosphere Watch network of monitoring stations.
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