Key Details
The WMO’s Greenhouse Gas Bulletin No. 22 reports global atmospheric concentrations. Its latest measurements cover 2025 for the major greenhouse gases; the hydrogen comparison runs through 2024.
Gas or Measure | Finding |
|---|---|
Carbon dioxide (CO₂) | 426.8 parts per million in 2025, 53% above the pre-industrial level; up 2.8 parts per million from 2024. |
Methane (CH₄) | 1,948 parts per billion in 2025, 167% above the pre-industrial level. |
Nitrous oxide (N₂O) | 339.1 parts per billion in 2025, 26% above the pre-industrial level. |
Combined warming influence | The warming effect of long-lived greenhouse gases increased 56% from 1990 to 2025; CO₂ accounted for about 81% of that increase. |
Sulfur hexafluoride (SF₆) | Reached 12.24 parts per trillion in 2025, about 249% higher than in 1995. Its increase during 2025 was a record high. |
Hydrogen (H₂) | Atmospheric concentration rose 5.3% between 2010 and 2024. The causes of this historical rise are not yet known. |
Slower Annual Growth Has Not Stopped Gas Accumulation
All three major gases reached record concentrations in 2025. CO₂ rose less sharply than during the exceptional 2023–24 increase, partly as land ecosystems recovered their ability to absorb carbon and fire-related emissions declined. But the 2.8-parts-per-million rise still added substantially to the CO₂ already in the atmosphere.
The distinction matters: emissions are gases released over a period; concentrations measure what has accumulated after natural absorption. A slower increase in concentration is not a decline in concentration.
Electricity Equipment Carries a Long-Lived Emissions Risk
SF₆ helps prevent electrical sparking in high-voltage equipment. Its concentration has risen as electricity infrastructure has expanded. Although present in tiny amounts, SF₆ has roughly 24,300 times CO₂’s warming potential over 100 years and can persist in the atmosphere for thousands of years. Gas held in existing equipment also poses a future risk if released during servicing or disposal. The WMO notes that substantially lower-warming alternatives are emerging.
Hydrogen Leaks Could Erode Climate Benefits
Hydrogen is not itself a direct greenhouse gas. In the atmosphere, however, it can affect chemical processes that remove methane and can contribute to the formation of other warming substances. This makes leakage from future hydrogen production, storage and transport a climate concern.
The WMO does not attribute the observed 2010–24 rise in atmospheric hydrogen to green-hydrogen projects; its causes remain uncertain. Its warning is forward-looking: a larger hydrogen economy will need to limit leaks to preserve its expected climate benefits. Separately, the bulletin shows how methane-isotope measurements can reveal changes in sources, including a likely wildfire-related shift in 2023–24, that methane concentrations alone would not explain.
Policy Relevance
The bulletin contains global observations, not an assessment of India’s emissions. Its relevance to India lies in two design choices as power networks and hydrogen projects expand:
Electrical infrastructure: Equipment selection, maintenance and end-of-life gas recovery can affect SF₆ emissions long after installation.
Hydrogen systems: Leak prevention and measurement matter alongside the emissions associated with producing hydrogen.
The findings also strengthen the case for sustained atmospheric monitoring. Measured concentrations and source-sensitive observations can complement emissions inventories, helping distinguish changes in human emissions from changes in natural absorption and other atmospheric processes.
Follow the Full Bulletin Here: WMO Greenhouse Gas Bulletin No. 22