GENEVA, 27 October 2026 — Greenhouse gas levels in the atmosphere reached unprecedented highs in 2025, the World Meteorological Organization said on Tuesday, with carbon dioxide at 426.8 parts per million — about 153 per cent of its pre-industrial level — and the UN weather agency warning that a powerful El Niño could push concentrations even higher this year, intensifying heatwaves, cyclones and rainstorms.
Illustration: An atmospheric monitoring station on a remote hilltop measuring greenhouse gases.
What Happened
The World Meteorological Organization (WMO) released its annual Greenhouse Gas Bulletin on Tuesday, 27 October 2026, reporting the latest measurements of the gases accumulating in the atmosphere. The global average concentration of atmospheric carbon dioxide reached 426.8 parts per million (ppm) in 2025, up 2.8 ppm from the previous year — a bigger annual increase than the average over the past decade, and about 153 per cent of the level in 1750, before the industrial era.
Concentrations of other important greenhouse gases also reached record highs in 2025. Methane stood at 267 per cent of its pre-industrial level and nitrous oxide at 126 per cent. The bulletin also raised concern about sulfur hexafluoride, or SF6, a greenhouse gas widely used in electrical equipment, saying its increase in 2025 was a record high. SF6 has a global warming potential more than 24,000 times that of carbon dioxide and can remain in the atmosphere for more than 1,000 years.
An important nuance: the report measures the amount of gas that accumulates in the atmosphere, not new annual emissions. That stock of gases is what traps heat, and it keeps growing as long as emissions exceed what oceans, forests and soils can absorb.
"Every additional part per million matters because it traps additional heat. In effect, we are supercharging the ocean and the atmosphere," WMO Deputy Secretary-General Ko Barrett said. "That means that heatwaves, tropical cyclones, and rainstorms are intensifying faster than our historical baselines prepared us for." The WMO noted that this year, parts of the world including Europe saw scorching summer temperatures, as well as devastating floods in Asia and elsewhere.
Background
The Greenhouse Gas Bulletin is the WMO's yearly check-up on the atmosphere, based on observations from its global monitoring network. Carbon dioxide is the most important long-lived greenhouse gas because it persists for centuries; methane is shorter-lived but far more potent per tonne over a 20-year horizon; nitrous oxide comes largely from agriculture and industry. Together, their rising concentrations are the main driver of the warming observed since the industrial era.
The bulletin lands just two weeks before the COP31 UN climate conference in Antalya, Turkey, scheduled for 9–20 November 2026, where the WMO said it will share its findings with negotiators. It also follows the UN Environment Programme's Emissions Gap Report 2026, released on 21 October, which concluded that breaching 1.5°C of warming is now unavoidable and that the goal must shift to keeping the overshoot as small and as short as possible.
The El Niño warning adds a further complication. El Niño warms the Pacific Ocean and disrupts weather patterns worldwide, typically bringing drier conditions to many regions. The WMO said it expected carbon dioxide concentrations to rise further this year due to fossil fuel burning and the onset of a powerful El Niño, which will cause drier weather and make it harder for carbon sinks — forests, soils and oceans — to absorb emissions.
Illustration: A parched, cracked-earth landscape under a harsh sun, showing drought conditions.
Why It Matters
Record concentrations matter because they lock in future warming. Even if emissions were cut sharply tomorrow, the gases already in the atmosphere would continue trapping heat for decades or centuries. The 2.8 ppm annual rise in carbon dioxide — faster than the decade average — suggests the world is not yet bending the curve, despite years of climate pledges and rapid growth in renewable energy.
The El Niño factor makes the near term worse. When carbon sinks weaken during dry El Niño years, a larger share of each year's emissions stays in the air, accelerating the rise. That feedback is one reason scientists watch El Niño years closely: they tend to produce temperature spikes, and they can make an already bad year measurably worse.
For negotiators heading to Antalya, the bulletin sharpens the stakes. The conference is billed as an "implementation COP", focused on turning existing pledges into concrete projects, with the second Global Stocktake beginning and climate finance high on the agenda. The WMO's numbers are a reminder that implementation is now racing against a physical clock: every year of delay adds parts per million that cannot easily be removed.
What Happens Next
The WMO will present the bulletin findings to negotiators at COP31 in Antalya, where countries will debate how to accelerate emissions cuts, scale up carbon dioxide removal, and support the most vulnerable nations. The summit's outcomes — particularly on finance and on the implementation of national climate plans — will show whether the political response is catching up with the atmospheric data.
Scientists will also watch how the expected El Niño develops. A powerful event would likely push 2026's carbon dioxide concentrations higher still, and could bring more extreme weather — droughts in some regions, floods in others — testing the resilience of communities already hit by this year's heat and floods.
Longer term, the bulletin points to two parallel tasks: cutting emissions fast enough to slow the annual rise, and developing removal methods at scale to draw down the stock already accumulated. Neither is optional, the WMO's message implies — the atmosphere keeps the score, and in 2025 it set another record.
Illustration: Planet Earth seen from space, wrapped in a glowing warming atmosphere.
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FAQ
What did the WMO report find?
Greenhouse gas concentrations hit record highs in 2025: carbon dioxide averaged 426.8 parts per million (about 153 per cent of the pre-industrial level), while methane reached 267 per cent and nitrous oxide 126 per cent of pre-industrial levels.
What is the difference between emissions and concentrations?
Emissions are the new gases released each year; concentrations are the total stock accumulated in the atmosphere. The WMO bulletin measures concentrations — the stock that actually traps heat — which keeps rising as long as emissions exceed what nature can absorb.
Why is El Niño a concern here?
A powerful El Niño is expected to bring drier weather that weakens carbon sinks such as forests and soils, so more of each year's emissions stays in the air, pushing concentrations higher.
What is sulfur hexafluoride (SF6)?
A greenhouse gas widely used in electrical equipment. Its increase in 2025 was a record high, according to the WMO; it warms the planet more than 24,000 times as powerfully as carbon dioxide per tonne and can persist for over 1,000 years.
What happens next?
The WMO will share the findings with negotiators at the COP31 climate conference in Antalya, Turkey, on 9–20 November 2026, where countries debate faster emissions cuts, carbon removal and climate finance.
Sources
- Reuters, "Greenhouse gases hit record highs, further rise expected with El Niño, UN weather agency says", 27 October 2026
- World Meteorological Organization, Greenhouse Gas Bulletin, October 2026 (as reported by Reuters)
- UN Environment Programme, Emissions Gap Report 2026: The Point of Return, 21 October 2026 (background)
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