WMO Reports Record Global Atmospheric Greenhouse Gas Levels in 2025
Surface concentrations of CO2, methane, and nitrous oxide reached historic highs, while trace gases like SF6 and hydrogen saw notable growth.
The World Meteorological Organization reported that globally averaged surface concentrations of carbon dioxide, methane, and nitrous oxide reached unprecedented highs in 2025, according to wmo.int 
wmo.intwmo.intwmo.intOpen source ↗. The globally averaged concentration of CO2 reached 426.8 parts per million, which stands at 153% of the pre-industrial baseline from 1750 wmo.intwmo.intwmo.intOpen source ↗. Measurements from the Global Atmosphere Watch network track the accumulation of gases in the atmosphere rather than gross annual emissions, with land ecosystems and oceans absorbing approximately half of emitted CO2 wmo.intwmo.intwmo.intOpen source ↗.
Concentration Dynamics and Radiative Forcing
Data from the NOAA Annual Greenhouse Gas Index indicates that radiative forcing caused by long-lived greenhouse gases grew by 56% between 1990 and 2025, with CO2 responsible for approximately 81% of this total increase wmo.intwmo.intwmo.intOpen source ↗. From 2024 to 2025, CO2 concentrations rose by 2.8 ppm, down from the surge observed in 2023–2024 following the recovery of terrestrial carbon sinks and lower fire activity wmo.intwmo.intwmo.intOpen source ↗. By comparison, the growth rate averaged 0.8 ppm annually in the 1960s and 2.4 ppm per year between 2011 and 2020 wmo.intwmo.intwmo.intOpen source ↗. Globally averaged methane levels reached 1,948 ppb, or 267% of the 1750 baseline, while nitrous oxide concentrations rose to 339.1 ppb, representing 126% of pre-industrial levels wmo.intwmo.intwmo.intOpen source ↗.
Trends in Trace Atmospheric Components
WMO also documented increases in atmospheric concentrations of sulfur hexafluoride and molecular hydrogen wmo.intwmo.intwmo.intOpen source ↗. SF6, primarily utilized as an electrical spark suppressant in power distribution, set an annual growth record in 2025 wmo.intwmo.intwmo.intOpen source ↗. The substance features an atmospheric lifetime exceeding 1,000 years and holds a 100-year global warming potential roughly 24,300 times greater than that of CO2 wmo.intwmo.intwmo.intOpen source ↗. Concurrently, atmospheric molecular hydrogen rose by 5.3% between 2010 and 2024 due to infrastructure leakage, presenting secondary warming impacts via altered atmospheric chemistry wmo.intwmo.intwmo.intOpen source ↗.
