Greenhouse gas levels in the atmosphere reached record highs in 2025, increasing the amount of heat trapped in the Earth's climate system, according to the World Meteorological Organization (WMO). Carbon dioxide, methane and nitrous oxide concentrations all rose to unprecedented levels, raising concerns about the long-term pace of global warming.

The WMO's Greenhouse Gas Bulletin, released in Geneva on Oct. 28, 2026, reported that global average carbon dioxide concentrations reached 426.8 parts per million in 2025. This was 153% of the pre-industrial level recorded in 1750.

Carbon Dioxide Levels Continue To Rise

Carbon dioxide is the main contributor to the warming effect of long-lived greenhouse gases. The WMO reported that global average concentrations increased by 2.8 parts per million between 2024 and 2025.

Although this increase was slightly smaller than the exceptional rise recorded in 2023-24, it remained substantial. The bulletin said carbon dioxide growth rates have tripled since the 1960s, rising from an average of 0.8 parts per million annually to 2.4 parts per million during the 2011-20 decade.

WMO Deputy Secretary-General Ko Barrett said greenhouse gases are trapping unprecedented amounts of heat. She also noted that carbon dioxide can affect the climate for decades and centuries because of its long atmospheric lifetime.

Methane And Nitrous Oxide Reach New Records

The report found that methane concentrations reached 1,948 parts per billion in 2025, equivalent to 267% of pre-industrial levels. Methane comes from natural sources, including wetlands, and human activities such as livestock farming, rice cultivation, fossil fuel production and waste disposal.

Nitrous oxide concentrations also reached a record 339.1 parts per billion. Sources include fertilizer use, industrial processes and biomass burning.

The report noted that greenhouse gas concentrations measure the amount accumulating in the atmosphere, rather than emissions released during a single year. About half of annual carbon dioxide emissions remain in the atmosphere, while land ecosystems and oceans absorb the rest.

Clean Energy Transition Faces Further Challenges

The WMO also highlighted rising levels of sulphur hexafluoride, a powerful greenhouse gas used in electricity distribution equipment. Its atmospheric lifetime exceeds 1,000 years.

The report stressed the importance of monitoring atmospheric changes as countries expand electricity systems and develop cleaner energy technologies.

It also identified hydrogen leakage as a concern because hydrogen can indirectly influence atmospheric warming, although it is not itself a greenhouse gas.

The findings underline the need to reduce greenhouse gas emissions and maintain reliable global monitoring. The data will also inform international climate discussions, including the UN climate conference scheduled for Antalya, Türkiye, in November 2026.