Greenhouse Gases Hit Record Highs in 2025: What the WMO Bulletin Says
The World Meteorological Organization (WMO) released its annual Greenhouse Gas Bulletin. It shows that the amounts of the three main long-lived greenhouse gases in the air reached new record highs in 2025.
Average carbon dioxide (CO₂) reached 426.8 ppm (parts per million), which is 53% above the level before 1750. Methane reached 1,948 ppb (parts per billion), 167% above pre-industrial levels. Nitrous oxide reached 339.1 ppb, 26% above pre-industrial levels.
CO₂ rose by 2.8 ppm from 2024 to 2025. This is lower than the record jump of 3.6 ppm in 2023–24, but still above the average of about 2.6 ppm a year in the previous decade.
The WMO linked the slower rise to land "carbon sinks" (forests and soils that soak up CO₂) recovering, and fewer fires, after the strong El Niño of 2023–24. It warned CO₂ may rise faster in 2026 because another strong El Niño is building, and that the ocean's ability to absorb CO₂ is at risk.
The warming effect of long-lived greenhouse gases rose by 56% between 1990 and 2025, with CO₂ responsible for about 81% of that increase. Sulphur hexafluoride (SF₆), an extremely powerful gas, recorded its largest yearly rise.
The bulletin is meant to guide climate negotiators at COP31 in Antalya, Türkiye, from 9 to 20 November 2026.
Greenhouse Effect: How Gases Trap Heat Around the Earth
The greenhouse effect is the natural process by which some gases in the air trap the Sun's heat and keep the Earth warm. Sunlight comes in and warms the ground, and the warm ground sends heat back towards space. Certain gases, called greenhouse gases, catch part of this outgoing heat and send it back down. Without this effect, the Earth would be a frozen planet. With too much of it, the Earth heats up, and that extra heating is what we call global warming.
The WMO bulletin measures exactly how strong the greenhouse "blanket" has become. Record levels of CO₂, methane and nitrous oxide in 2025 mean more heat is trapped every year, and because CO₂ stays for centuries, the warming they cause is locked in long into the future.
World Meteorological Organization (WMO)
The World Meteorological Organization is the United Nations body for weather, climate and water. It helps countries share weather data, sets common standards for measuring weather, and publishes global reports on the state of the climate. Its headquarters is in Geneva, Switzerland. It runs a worldwide network that measures greenhouse gases and publishes the results every year.
The record numbers come from WMO's Greenhouse Gas Bulletin, built on measurements from its Global Atmosphere Watch network, and they are released just before COP31 to inform climate negotiations.
Global Warming Potential (GWP): Comparing the Warming Power of Gases
Global Warming Potential, or GWP, tells us how much heat a gas traps compared with carbon dioxide, which is given a GWP of 1. If a gas has a GWP of 1,000, releasing 1 kg of it warms the Earth as much as releasing 1,000 kg of CO₂ over the same period. GWP is usually measured over 100 years. It lets countries add up different gases into one figure called CO₂-equivalent.
The bulletin flagged a record increase in SF₆ in 2025. Even though SF₆ exists in tiny amounts, its huge GWP and very long lifetime mean every extra tonne adds warming for many centuries.
- CO₂ in 2025: 426.8 ppm, 53% above pre-industrial (153% of the 1750 level)
- Methane in 2025: 1,948 ppb, 167% above pre-industrial (267% of the 1750 level)
- Nitrous oxide in 2025: 339.1 ppb, 26% above pre-industrial; up 1.1 ppb from 2024
- CO₂ rise 2024–25: 2.8 ppm; record rise 2023–24: 3.6 ppm; 2011–2020 average: about 2.4 ppm a year; 1960s: about 0.8 ppm a year
- Warming effect (radiative forcing) of long-lived greenhouse gases up 56% from 1990 to 2025; CO₂ about 81% of the increase
- Methane sources: about 65% human, about 35% natural
- The past 11 years have been the warmest on record
- Atmospheric hydrogen rose 5.3% between 2010 and 2024
- COP31: Antalya, Türkiye, 9 to 20 November 2026