The global average concentration of CO2 is now 53% higher than pre-industrial levels, and it’s not the only greenhouse gas of concern.
New year, new records for atmospheric concentrations of the three main greenhouse gases. Carbon dioxide, methane and nitrous oxide have reached unprecedented levels in 2025, and now trap an unimaginable amount of heat that energizes extreme weather phenomena.
The cold shower comes from the latest greenhouse gas bulletin from the World Meteorological Organization, published to provide scientific information to the negotiators of the Climate Conference of the Parties (COP31) to be held in Antalya, Turkey, from 9 to 20 November.
Growth destined to continue
The global average concentration of CO2 is now 426.8 parts per million, that of methane (CH4) is 1,948 parts per billion, and nitrous oxide (N20) is 339.1 parts per billion. These are increases of 53%, 167% and 26% respectively compared to the pre-industrial era, i.e. compared to before 1750.
A series of negative records destined to continue, because the bulletin reports the overall and progressive accumulation of greenhouse gases and not the annual emissions, and CO2 can remain in the atmosphere for very long periods. Every year, approximately half of the total CO2 emitted remains in the atmosphere, while the remainder is absorbed by the oceans and terrestrial ecosystems.
Tripled since the 1960s
CO2 growth rates have tripled since the 1960s, going from an average annual increase of 0.8 ppm to 2.4 ppm in just the decade from 2011 to 2020. From 2024 to 2025, the global average CO2 concentration increased by 2.8 ppm, higher than the 10-year average but slightly lower than the 2023/2024 surge (when it increased of 3.5 parts per million).
“The more modest growth rate from 2024 to 2025 reflects the recovery of terrestrial carbon sinks and the reduction of carbon emissions from fires after the strong El Niño of 2023/2024, which had reduced the efficiency of the biosphere through increased drought, drier vegetation and a greater number of forest fires,” explained Oksana Tarasova, science officer at the WMO. For the same reasons, an increase in the rate of growth of concentrations in 2026 is plausible, also due to the effect of the super El Niño on terrestrial carbon sinks.
As Maurizio Maugeri, full professor of Physics of the Earth, Planets, Space and Climate system at the University of Milan, explained in commenting on the last report: «When we start cutting emissions, the first effect we will notice will be the reduction in the growth rate of CO2. The concentration, however, will begin to stabilize only when we manage to achieve net zero emissions (i.e. when the CO2 entering the atmosphere, including that emitted by man, will no longer be greater than that which the Earth itself is able to absorb, plus that which we may eventually be able to remove artificially with appropriate technologies)”.
The impact on global warming
From 1990 to 2025, the warming effect on the climate due to greenhouse gases increased by 56%, and 81% of this effect depends on CO2. 16% is instead due to methane, which however has a much shorter duration of stay in the atmosphere.
This gas is emitted largely by human activities (livestock breeding, rice cultivation, use of fossil fuels, emissions from landfills, biomass combustion) and partly by natural systems, such as swamps and peat bogs. Nitrous oxide, on the other hand, derives from industrial processes, use of fertilizers and biomass combustion processes.
Two gases to monitor
Finally, the document called for more careful monitoring of two other long-lasting and potentially problematic gases, linked to the production and distribution of electricity and whose concentration is therefore destined to increase with decarbonisation.
The first is molecular hydrogen (H2), a gas used for energy storage, whose concentration increased by 5.3% between 2010 and 2024. It is not a greenhouse gas, but it influences the chemistry of the atmosphere, indirectly promoting global warming, and what is worrying are its losses from gas pipelines, production and storage plants.
The second gas is sulfur hexafluoride (SF6), used as a spark suppressor in electricity distribution. Its levels have increased steadily over the last three decades and this gas, which remains in the atmosphere for a thousand years, has the highest 100-year global warming potential, approximately 24,300 times that of CO2.
Monitoring atmospheric composition in the coming years will help ensure that the benefits of the energy transition are not attenuated by gases with less than desirable effects.
