Geneva:Global concentrations of carbon dioxide (CO2), methane, and nitrous oxide reached unprecedented levels in 2025, raising concerns about extreme weather risks and threats to economies and societies, as warned by the World Meteorological Organization (WMO).
According to United News of Bangladesh, the WMO's latest Greenhouse Gas Bulletin revealed that the average global concentration of CO2 last year was 426.8 parts per million (ppm), marking 153 percent of the pre-industrial level from 1750. WMO Deputy Secretary-General Ko Barrett emphasized the increasing intensity of heatwaves, tropical cyclones, and rainstorms, attributing these changes to the supercharged ocean and atmosphere.
The bulletin also reported record concentrations of methane and nitrous oxide in 2025, the second and third most significant long-lived greenhouse gases from human activities. Barrett highlighted the unprecedented heat being trapped in the atmosphere, which fuels extreme weather and poses risks to economies and societies. She noted that the past 11 years were the warmest on record, with the trend expected to persist due to the long-lasting effects of CO2 in the atmosphere.
The bulletin documented the acceleration of CO2 accumulation, tripling since the 1960s. A strong El Niño event in 2023-2024 contributed to a 3.5 ppm increase by weakening the biosphere's carbon absorption capacity. Although the annual rise slowed to 2.8 ppm in 2024-2025, it represented a significant addition of carbon from fossil fuels. WMO senior scientific officer Oksana Tarasova warned of potential further increases in CO2 levels in 2026 due to ongoing fossil fuel use and another powerful El Niño.
The WMO measures greenhouse gas accumulation rather than annual emissions, with around half of the CO2 emitted each year remaining in the atmosphere. The US National Oceanic and Atmospheric Administration's index shows a 56 percent increase in the warming effect of greenhouse gases on the climate between 1990 and 2025, with CO2 accounting for 81 percent of the increase.
As nations transition to cleaner energy systems, the WMO advises close monitoring of molecular hydrogen (H2) and sulphur hexafluoride (SF6), gases linked to electricity production and distribution. SF6, used in power systems, has seen increased use over three decades and poses a significant global warming potential. Hydrogen, employed in energy storage and hard-to-decarbonize sectors, presents concerns due to potential leakage.
The agency warns that hydrogen leakage and SF6's long atmospheric lifetime could undermine climate benefits from the energy transition. Continuous atmospheric monitoring is essential to prevent unintended consequences of changes in energy systems. The WMO releases this bulletin to provide scientific evidence for the UN climate conference, with COP31 set to take place in Antalya, Trkiye, from November 9 to 20, aiming to turn climate commitments into actions.