WASHINGTON (dpa-AFX) - Levels of carbon dioxide and other major greenhouse gases in the atmosphere caused by burning fossil fuels reached record highs in 2025, locking in more long-term global warming, the World Meteorological Organization (WMO) said on Tuesday.
The agency's latest Greenhouse Gas Bulletin indicates an average global concentration of CO2 at 426.8 parts per million (ppm) last year, or 153 per cent of the 1750 pre-industrial baseline.
'Every additional part per million matters because it traps additional heat. In effect, we are supercharging the ocean and the atmosphere. That means that heat waves, tropical cyclones, and rainstorms are intensifying faster than our historical baselines prepared us for,' WNO Deputy Secretary-General Ko Barrett said at a news conference in Geneva.
Equally worrying, levels of methane and nitrous oxide - the second and third most important long-lived greenhouse gases caused by human activities - also hit a new peak in 2025.
'Another year, another new record. Greenhouse gases are trapping an unprecedented amount of heat in the atmosphere, providing energy for more extreme weather and associated risks to our economies and societies,' Barrett stressed.
'The past 11 years have been the warmest on record and this trend is set to continue. CO2 has a very long lifetime and so will affect the global climate not just for years but for decades and even centuries.'
When the Bulletin was first published in 2004, the annual average level of CO2 measured by WMO's Global Atmosphere Watch network of monitoring stations was 377.5 ppm, compared with nearly 427 ppm today.
Growth rates of CO2 have tripled since the 1960s, accelerating from an annual average increase of 0.8 ppm per year to 2.4 ppm per year in the decade from 2011 to 2020.
The 'exceptional [3.5 ppm] surge' of 2023-2024 coincided with a strong El Niño 'which reduced the efficiency of the biosphere through more drought, drier vegetation and more wildfires', said WMO senior scientific officer Oksana Tarasova.
She noted that although the 2.8 ppm annual increase from 2024-2025 represented a more modest increase, it was nonetheless 'a substantial addition of carbon to the atmosphere from fossil fuel burning. We can expect to see a further increase in concentrations in 2026 because of fossil fuel burning and the development of a powerful El Niño which will impact land carbon sinks as it did in 2023-2024.'
The U.S. National Oceanic and Atmospheric Administration (NOAA) Annual Greenhouse Gas Index shows that from 1990 to 2025, the warming effect on our climate caused by greenhouse gases increased by 56 per cent, with CO2 accounting for about 81 per cent of this increase, known as 'radiative forcing'.
WMO noted that as countries transform their energy systems towards decarbonization, careful attention should be given to two potent but less abundant trace gases closely related to electricity production and distribution: molecular hydrogen (H2) and sulphur hexafluoride (SF6).
WMO releases the Bulletin to provide authoritative scientific data for negotiators attending the upcoming annual UN Climate conference, which is scheduled to be held in Antalya, Türkey, from November 9 to 20.
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