Atmospheric concentrations of carbon dioxide, methane and nitrous oxide reached record levels in 2025, according to the World Meteorological Organization. Global CO₂ concentrations rose to 426.8 ppm, raising concerns over long-term warming and the climate implications of energy technologies.
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Greenhouse gas concentrations reach new records in 2025
Atmospheric levels of carbon dioxide, methane and nitrous oxide reached new record highs in 2025, according to the latest Greenhouse Gas Bulletin published by the World Meteorological Organization (WMO).
The global average CO₂ concentration reached 426.8 parts per million (ppm) in 2025, equivalent to 153% of its pre-industrial level in 1750.
“Another year, another record,” said Ko Barrett, WMO Deputy Secretary-General. “Greenhouse gas emissions are trapping unprecedented amounts of heat in the atmosphere, leading to increasingly extreme weather conditions and increasing risks to our economies and societies.”
The problem is particularly significant for CO₂, which remains in the atmosphere for extremely long periods, contributing to global warming for centuries.
CO₂ concentrations continue to rise rapidly
The latest WMO data show that the rate of increase in atmospheric CO₂ concentrations has tripled since the 1960s. Average annual growth rose from 0.8 ppm to 2.4 ppm between 2011 and 2020.
Between 2024 and 2025, concentrations increased by 2.8 ppm, exceeding the average recorded over the past decade but remaining slightly below the peak observed between 2023 and 2024.
The slower growth in CO₂ concentrations between 2024 and 2025 was linked to a recovery in the carbon absorption capacity of terrestrial ecosystems and a reduction in wildfire emissions. During 2023 and 2024, El Niño had intensified droughts and wildfires, reducing the biosphere’s capacity to absorb carbon.
“An annual increase of 2.8 ppm is still a significant addition of carbon to the atmosphere from the burning of fossil fuels,” explained Oksana Tarasova, Senior Scientific Officer at WMO.
Greenhouse gas concentrations could rise further in 2026
For 2026, WMO expects atmospheric concentrations to increase further, driven by fossil fuel emissions and the possible development of another strong El Niño event, which could affect the ability of terrestrial ecosystems to absorb CO₂.
“There are also increasing risks of reduced CO₂ uptake by the oceans in a continuously changing climate,” Tarasova added.
Energy transition and the risk of indirect emissions
The WMO report also draws attention to two gases associated with the energy system: sulphur hexafluoride (SF₆), primarily used in electrical equipment, and hydrogen.
Sulphur hexafluoride is a particularly potent greenhouse gas, with a 100-year global warming potential approximately 24,300 times greater than that of carbon dioxide and an atmospheric lifetime exceeding 1,000 years. Its annual increase reached a new record in 2025.
Hydrogen, by contrast, is not itself a greenhouse gas, but it can influence atmospheric chemistry and contribute indirectly to warming. Its atmospheric concentration increased by 5.3% between 2010 and 2024. Potential hydrogen leakage during production, transport and storage therefore requires monitoring.
According to WMO, monitoring these substances is essential to prevent the indirect effects of energy infrastructure from undermining some of the expected benefits of decarbonisation.
The latest record in greenhouse gas concentrations once again highlights the need to reduce emissions and accelerate the energy transition, while paying particular attention to the climate impacts of the technologies involved.
The issue is especially relevant ahead of COP31, scheduled to take place from 9 to 20 November in Antalya, Türkiye.
