GENEVA, October 27 — Atmospheric concentrations of the three principal long-lived greenhouse gases reached their highest levels on record in 2025, locking in additional planetary warming that will persist for generations, the World Meteorological Organization said with the release of its latest annual Greenhouse Gas Bulletin.
The globally averaged surface concentration of carbon dioxide stood at 426.8 parts per million, while methane measured 1,948 parts per billion and nitrous oxide 339.1 parts per billion. Compared with pre-industrial baselines before 1750, carbon dioxide is up 53 percent, methane 167 percent and nitrous oxide 26 percent. Carbon dioxide alone accounts for roughly two-thirds of the cumulative warming effect from long-lived greenhouse gases.
The rise in carbon dioxide from 2024 to 2025 was 2.8 parts per million — below the exceptional 3.6 ppm surge recorded between 2023 and 2024, but above the average annual growth of 2.6 ppm over the past decade and far above the 0.8 ppm typical in the 1960s. About half of the carbon dioxide emitted each year remains in the atmosphere; the rest is taken up by land ecosystems and oceans.
Scientists attribute the slightly milder year-over-year increase to a recovery in natural land carbon sinks after the strong El Niño of 2023–2024, which had dried vegetation and intensified wildfires. They warn, however, that a powerful El Niño developing in 2026 is likely to weaken those sinks again and drive a fresh jump in concentrations.
The bulletin also spotlighted two potent but less abundant trace gases tied to the energy transition. Sulphur hexafluoride, used as an insulating medium in electrical equipment, has risen 249 percent above its 1995 level; though present in tiny amounts, it has an atmospheric lifetime of up to 3,200 years and a warming potential more than 24,000 times that of carbon dioxide.
The findings land weeks before the COP31 climate summit, scheduled to open in Antalya, Turkey, on November 9, where negotiators will confront the widening gap between emissions pledges and the trajectory of the atmosphere.