The globally averaged concentration of carbon dioxide (CO₂) in the atmosphere was 426.8 parts per million (ppm) in 2025, a new record high, according to the World Meteorological Organization’s Greenhouse Gas Bulletin released on October 27, 2026.
That is 153% of the preindustrial level of 1750. CO₂ rose by 2.8 ppm from 2024 to 2025, less than the exceptional jump of 2023 to 2024 but above the 2.4 ppm yearly average for 2011–2020; in the 1960s the rate was 0.8 ppm a year. The WMO links the slower rise to land carbon sinks recovering and fewer wildfire emissions after the strong 2023/2024 El Niño. Methane (1,948 parts per billion, 267% of 1750) and nitrous oxide (339.1 ppb, 126%) also hit records. When the bulletin began in 2004, CO₂ stood at 377.5 ppm. The WMO expects concentrations to keep rising in 2026 because of fossil fuel burning and a developing El Niño, and the report comes ahead of the COP31 climate talks in Antalya, Turkey, on November 9–20.
Image: NOAA’s Mauna Loa Observatory, Hawaii. Photo by Brian Vasel/NOAA, public domain, via Wikimedia Commons.