WMO Reports Record Greenhouse Gas Levels in 2025 as CO₂ Reaches 426.8 ppm

Atmospheric concentrations of carbon dioxide, methane, and nitrous oxide reached unprecedented levels in 2025, trapping more heat in Earth's atmosphere and reinforcing the long-term impacts of climate change, according to the World Meteorological Organization (WMO). Released on 27 October 2026, the organization's latest Greenhouse Gas Bulletin reported that global average carbon dioxide (CO₂) concentrations reached 426.8 parts per million (ppm), about 53% higher than pre-industrial levels in 1750.

The findings come ahead of the COP31 UN Climate Change Conference in Antalya, Türkiye, scheduled for 9–20 November 2026. WMO warns that continued greenhouse gas accumulation is driving global warming and increasing the risks of extreme weather. The report also highlights the importance of monitoring emerging atmospheric changes as countries expand renewable electricity networks and low-carbon energy technologies.

 

Carbon Dioxide Concentrations Reach 426.8 ppm

 

Global average atmospheric CO₂ concentrations rose by 2.8 ppm between 2024 and 2025, exceeding the longer-term average growth rate, though still below the exceptional increase recorded between 2023 and 2024. According to WMO, annual CO₂ growth rates have tripled since the 1960s, rising from an average of 0.8 ppm annually to 2.4 ppm during the 2011-2020 decade.

Carbon dioxide remains the largest contributor to human-driven climate warming because it is abundant and has a long atmospheric lifetime. WMO Deputy Secretary-General Ko Barrett warned, "Another year, another new record." She highlighted how greenhouse gases continue to trap heat and increase risks to economies and societies. WMO also noted that the past 11 years have been the warmest on record, and that accumulated atmospheric CO₂ will continue to influence the climate for decades and centuries.

 

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Methane and Nitrous Oxide Also Reach Record Highs

 

Methane concentrations reached a global average of 1,948 parts per billion (ppb) in 2025, equivalent to 267% of their pre-industrial concentration. Methane accounts for approximately 16% of the warming effect from long-lived greenhouse gases. About 65% of methane emissions come from human activities, including livestock farming, rice cultivation, fossil fuel operations, landfills, and biomass burning, while natural sources, such as wetlands, account for the remaining 35%.

Nitrous oxide concentrations also reached a record 339.1 ppb, approximately 26% above pre-industrial levels. Emissions originate from both natural processes and human activities, particularly agricultural fertilizer use, biomass burning and industrial operations. The continued rise in both gases highlights the need to address emissions across agriculture, waste management, industrial production, and energy systems alongside efforts to reduce carbon dioxide.

 

Carbon Sinks Influence Atmospheric CO₂ Growth

 

WMO estimates that approximately half of the carbon dioxide emitted annually remains in the atmosphere, while land ecosystems and oceans absorb much of the remainder. However, the effectiveness of these natural carbon sinks varies with temperature, rainfall, drought and wildfire activity. The organization attributes the relatively slower increase in atmospheric CO₂ during 2025 partly to a recovery in land carbon absorption and reduced wildfire emissions following the strong El Niño conditions of 2023–2024.

Oksana Tarasova, Senior Scientific Officer at WMO, said, "However, a 2.8 ppm annual increase is still a substantial addition of carbon to the atmosphere from fossil fuel burning." She warned that continued fossil fuel consumption and a strong El Niño could drive further increases in atmospheric CO₂ in 2026. WMO also noted growing concerns about reduced ocean carbon uptake as the climate changes.

 

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Greenhouse Gas Accumulation Increases Long-Term Warming

 

The report distinguishes atmospheric greenhouse gas concentrations from annual emissions. Emissions measure the amount of gases released during a period, while concentrations reflect the gases accumulated in the atmosphere. Consequently, a slower annual increase does not necessarily mean declining concentrations, and atmospheric greenhouse gas levels can keep rising even if the growth rate temporarily slows.

According to the US National Oceanic and Atmospheric Administration's Annual Greenhouse Gas Index, the warming influence, or radiative forcing, of long-lived greenhouse gases increased by 56% between 1990 and 2025. Carbon dioxide accounted for approximately 81% of that increase. These findings show that cumulative emissions continue to intensify climate warming, reinforcing the need for sustained reductions across energy production, industry, transport, and agriculture.

 

Hydrogen and SF₆ Raise New Energy Transition Monitoring Concerns

 

WMO also highlighted two gases requiring closer monitoring as energy systems evolve: sulfur hexafluoride (SF₆) and molecular hydrogen (H₂). SF₆ is commonly used as an insulating and arc-suppression gas in electrical equipment. It has an atmospheric lifetime exceeding 1,000 years and a 100-year global warming potential approximately 24,300 times greater than carbon dioxide. The WMO reported that atmospheric SF₆ reached a record high in 2025.

Hydrogen concentrations increased by approximately 5.3% between 2010 and 2024. Although hydrogen is not classified as a direct greenhouse gas, atmospheric leakage can influence chemical processes that indirectly contribute to warming. As hydrogen technologies expand into industrial production, transport and energy storage, WMO emphasizes the importance of monitoring leakage throughout production, transportation and storage infrastructure.

The latest findings reinforce the importance of accurate atmospheric monitoring and sustained reductions in greenhouse gas emissions. WMO's Global Atmosphere Watch network provides internationally coordinated measurements that allow scientists to track long-term concentration trends and investigate changes in natural and human-caused sources.

With COP31 approaching, the report provides scientific evidence that greenhouse gases continue to accumulate despite global decarbonization efforts. Reducing emissions, protecting natural carbon sinks, and monitoring the environmental impacts of emerging energy technologies will remain essential to limiting long-term climate risks.

 

Source: World Meteorological Organization (WMO)