WMO: Atmospheric carbon dioxide reached record high in 2025

The World Meteorological Organization (WMO) has published its Greenhouse Gas Bulletin on global greenhouse gas levels. The report says that in 2025, levels of carbon dioxide and other key greenhouse gases in the atmosphere reached unprecedented highs. The global average surface carbon dioxide concentration reached 426.8 parts per million in 2025, which is 153% of the pre-industrial baseline in 1750. Methane and nitrous oxide concentrations linked to human activity also rose to new records.

The report notes that about half of the total carbon dioxide emitted each year remains in the atmosphere, while the rest is absorbed by land ecosystems and oceans. The carbon dioxide growth rate has tripled since the 1960s, and the global average concentration rose by 2.8 ppm from 2024 to 2025.

WMO Deputy Secretary-General Ko Barrett said greenhouse gases are trapping unprecedented amounts of heat, fuelling more extreme weather and risks for economies and societies, and that the 11 hottest years on record have now passed. WMO Senior Scientific Officer Oksana Tarasova said the milder rise between 2024 and 2025 reflects the recovery of land carbon sinks after the strong 2023/2024 El Niño and fewer fire emissions. Tarasova added that further increases in carbon concentrations may be seen in 2026.