WMO: Carbon dioxide concentration hit record 426.8 ppm in 2025
Carbon dioxide, methane and nitrous oxide in the atmosphere reached new highs, the WMO's Greenhouse Gas Bulletin says. The agency expects another rise in 2026 because of El Niño.
Symbolic image · Photo: Htm / Wikimedia Commons, CC BY-SA 3.0 (cropped and resized)
Greenhouse gas concentrations in the atmosphere have reached another record. According to the annual bulletin of the World Meteorological Organization (WMO), presented in Geneva on Tuesday, globally averaged CO2 stood at 426.8 ± 0.2 parts per million (ppm) in 2025 – 153% of the pre-industrial level of 1750. Methane reached 1,948 ± 2 parts per billion (ppb) and nitrous oxide 339.1 ± 0.1 ppb. The figures are measurements from the Global Atmosphere Watch network, not model results.
CO2 rose by 2.8 ppm from 2024 to 2025 – above the average of the past decade but below the record jump a year earlier. WMO senior scientific officer Oksana Tarasova said land carbon sinks recovered after the 2023/2024 El Niño and fire emissions fell. Still, 2.8 ppm is "still a substantial addition of carbon" from burning fossil fuels, she said. According to an index by the U.S. agency NOAA, the warming effect of long-lived greenhouse gases has risen by 56% since 1990.
For 2026, the WMO expects a further increase because the developing El Niño could again weaken uptake by vegetation – a projection, not a measurement. "Another year, another new record," WMO Deputy Secretary-General Ko Barrett said. The bulletin is meant to inform negotiators at the COP31 climate conference in Antalya, Türkiye, from Nov. 9 to 20.