The World Meteorological Organisation (WMO) reported that atmospheric carbon dioxide (CO2) reached an average of 426.8 parts per million in 2025, representing a 153 % increase over the 1750 pre‑industrial baseline.

WMO Deputy Secretary‑General Ko Barrett said each additional ppm traps more heat, effectively “supercharging” the ocean and atmosphere and intensifying heatwaves, tropical cyclones and rainstorms.

Methane and nitrous oxide also set new records in 2025, adding to the heat‑trapping effect and raising concerns about economic and societal risks.

The Bulletin notes that CO2’s long atmospheric lifetime means its climate impact will persist for decades to centuries, with the past 11 years already the warmest on record.

Since the 1960s, the annual CO2 growth rate has tripled from 0.8 ppm to 2.4 ppm per year in the 2011‑2020 decade, and a 3.5 ppm surge in 2023‑2024 coincided with a strong El Niño that reduced biosphere efficiency.

WMO senior scientific officer Oksana Tarasova warned that a modest 2.8 ppm increase in 2024‑2025 still represents a substantial addition of carbon from fossil‑fuel burning, and further rises are expected in 2026 due to continued emissions and another El Niño.

About half of annual CO2 emissions remain in the atmosphere while the rest is absorbed by land and oceans, underscoring the limited capacity of natural sinks to offset rising concentrations.

The WMO highlighted emerging concerns around trace gases linked to the energy transition, noting record‑high sulphur hexafluoride (SF6) in 2025—an ultra‑potent greenhouse gas with a 1,000‑year lifetime—and a 5.3 % rise in hydrogen concentrations between 2010 and 2024.

While hydrogen itself is not a greenhouse gas, the WMO warned that leaks from production, pipelines and storage can alter atmospheric chemistry and indirectly amplify warming.

The Bulletin is intended to supply authoritative data for negotiators at the upcoming COP31 climate conference in Antalya, Turkey, scheduled for 9‑20 November, where parties aim to translate commitments into concrete action.