"WMO Greenhouse Gas Bulletin: CO2 Hits 426.8 ppm While Clean Energy Additions Stall"

Two announcements landed in the same week, and they belong in the same sentence. On 27 October 2026, the World Meteorological Organization (WMO) reported that the atmosphere's main greenhouse gases all reached record concentrations in 2025. Days earlier, at the Singapore International Energy Week, the head of the International Renewable Energy Agency (IRENA) said the world will add less clean-energy capacity in 2026 than it did in 2025 — the first decline in five years. The air is getting thicker with heat-trapping gas at the exact moment the machine built to stop it is slowing down.

The WMO's Greenhouse Gas Bulletin, its 22nd annual edition, puts the numbers plainly. Carbon dioxide averaged 426.8 parts per million in 2025, methane 1,948 parts per billion, and nitrous oxide 339.1 parts per billion — each a record, each higher than the year before.

The detail inside the headline matters. CO2 rose by 2.8 ppm between 2024 and 2025, less than the 3.6 ppm surge of the year before — a slowdown the WMO links to recovering land carbon sinks and lower fire emissions after the strong 2023–2024 El Niño. But 2.8 ppm is still above the past decade's average growth rate of 2.6 ppm, and nearly four times the 0.8 ppm annual pace of the 1960s. WMO senior scientific officer Oksana Tarasova put it plainly: a 2.8 ppm annual increase is still a substantial addition of carbon to the atmosphere from fossil fuel burning. When the bulletin was first published in 2004, CO2 stood at 377.5 ppm. The comparison that should alarm anyone is not one year against the next, but 377.5 against 426.8.

Deputy Secretary-General Ko Barrett's warning was blunter than the numbers: every additional part per million matters because it traps additional heat, supercharging the ocean and the atmosphere, so that heat waves, tropical cyclones and rainstorms intensify faster than historical baselines prepared us for. The past 11 years have been the warmest on record, and the trend is expected to continue. CO2 has a very long lifetime, she noted, and will affect the climate not just for years but for decades and centuries.

There is also a quieter warning tucked into the bulletin. Two gases closely tied to electricity production and distribution are rising: molecular hydrogen, for reasons not yet understood, and sulfur hexafluoride (SF6), a spark suppressant in electrical equipment, which saw its largest annual increase in 2025. SF6 has an atmospheric lifetime of up to 3,200 years and a warming potential more than 24,000 times that of CO2. The energy transition is essential and welcome, Barrett said, but it needs to be done in a smart way, informed by environmental observations. Even the tools of decarbonization come with an atmospheric footprint if nobody watches them.

That is what makes the IRENA announcement sting. Clean power installations surged a record 692 gigawatts, or 15.5%, in 2025, taking total clean capacity to 5,149 GW — half the world's power capacity. Yet IRENA Director-General Francesco La Camera told Reuters that 2026 will not set a new record, because generation capacity has outrun the grids meant to carry it. China, the world's biggest renewable energy producer, turned away enough clean energy in the first half of 2026 to power Mexico for a year, while networks in Australia and Japan also failed to keep pace. La Camera said growth elsewhere is unlikely to offset the slowdown in China, and declined to give a numerical forecast. The constraint, in other words, has moved: it is no longer mainly about building solar panels and wind turbines, but about wires, permits and curtailment rules.

Read together, the two reports describe a bottleneck, not a mystery. The atmosphere keeps score in parts per million, not in pledges, and the WMO bulletin will be on the table when negotiators meet next month at the COP31 climate conference in Antalya, Türkiye — weeks after the United Nations warned that urgent and stringent emission cuts are required. Wires can be built and rules rewritten on a political timetable; 426.8 ppm cannot be un-emitted on one. I expect IRENA's 2026 tally, when it is published, to confirm the first annual decline in clean-energy additions since 2021, coming in below 2025's 692 GW. If that proves wrong, it will most likely be because grid connections accelerated faster than the transmission bottleneck suggests — a welcome way to be wrong. But the direction of the record is not in doubt: the longer the grid lags the buildout, the longer each year's bulletin reads the same way, only higher.