The World Meteorological Organization reports record greenhouse gas concentrations in 2025, warning of growing climate risks as CO₂ levels continue to rise and the energy transition faces new challenges.
By Laura Contemori
Greenhouse gas concentrations reach record levels in 2025
Atmospheric concentrations 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 the pre-industrial reference level recorded in 1750.
“Another year, another record,” said Ko Barrett, Deputy Secretary-General of the WMO.
“Greenhouse gas emissions are trapping unprecedented amounts of heat in the atmosphere, leading to increasingly extreme weather conditions and raising risks for our economies and societies,” Barrett warned.
The concern is particularly significant for CO₂, which remains in the atmosphere for a very long time, 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 in the 1960s 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 between 2024 and 2025 was linked to a recovery in the capacity of terrestrial ecosystems to absorb carbon and a reduction in wildfire emissions.
During the 2023-2024 El Niño event, intensified droughts and wildfires had weakened the biosphere’s ability to absorb CO₂.
“An annual increase of 2.8 ppm still represents a significant addition of carbon to the atmosphere from the burning of fossil fuels,” explained Oksana Tarasova, Senior Scientific Officer at the WMO.
Looking ahead to 2026, the organisation expects atmospheric CO₂ concentrations to rise further, driven by fossil fuel emissions and the possible development of another strong El Niño event.
Such an event could affect the ability of terrestrial ecosystems to absorb carbon dioxide.
“There are also growing risks of reduced CO₂ uptake by the oceans as the climate continues to change,” Tarasova added.
Energy transition raises concerns over indirect emissions
The WMO report also highlights two gases associated with the energy system: sulphur hexafluoride (SF₆), primarily used in electrical equipment, and hydrogen.
Sulphur hexafluoride is an extremely powerful greenhouse gas, with a 100-year global warming potential approximately 24,300 times greater than 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 indirectly contribute to global warming.
Its atmospheric concentration increased by 5.3% between 2010 and 2024. Potential hydrogen leaks during production, transport and storage therefore require monitoring.
According to the WMO, monitoring these substances is essential to prevent indirect emissions from energy infrastructure from undermining some of the expected benefits of decarbonisation.
The latest record once again highlights the need to reduce greenhouse gas emissions and accelerate the energy transition, while carefully considering the climate impacts of the technologies being deployed.
The issue is particularly relevant ahead of COP31, scheduled to take place from 9 to 20 November in Antalya, Türkiye.
