By Roxby Hartley, Ph.D., Climate Risk Director, EcoEngineers

I spend a fair amount of time looking at greenhouse gas data. I know, it’s weird but true. While most attention goes to carbon dioxide, methane has rightly become a major industry focus. Nitrous oxide is attracting more attention, as well. However, sulfur hexafluoride (SF₆) rarely gets a mention outside specialist circles.

Recently, Stephan, a longtime contributor on the Arctic Sea Ice Forum, posted the latest update of National Oceanic and Atmospheric Administration’s (NOAA’s) atmospheric SF₆ measurements. Stephan has tracked this dataset closely for years and regularly posts updates.

National Oceanic and Atmospheric Administration

You don’t have to be a rocket scientist to be worried by that sharp increase in 2025. Not because concentrations are rising, because nearly every greenhouse gas chart seems capable of managing that. It’s the sudden uptick that is the worry.

SF₆ is not some newly discovered environmental problem. Utilities know about it. Regulators know about it. Manufacturers know about it. Alternative technologies already exist, and Europe is actively moving to restrict its use in new equipment.

So why does the atmospheric record appear to be moving sharply in the wrong direction? The answer is simple: most SF₆ is used in electrical transmission and distribution equipment. Switchgear, substations and transmission assets have relied on it for decades because it is exceptionally good at insulating high voltage systems and suppressing electrical arcs.

The obvious assumption is that emissions should begin falling as alternatives become available. Yet the atmosphere appears to be telling a different story. The explanation is scale.

The world already contains an enormous installed bank of SF₆. Much of that equipment was installed years or decades ago and is expected to remain in service for decades more. Substations are not like smartphones. They cannot be replaced simply because a better model exists. So, if the world is moving away from SF₆, is anyone still producing it? The answer appears to be yes.

However, finding reliable production figures is surprisingly difficult. Atmospheric measurements are easier to find than production statistics. What is clear is that enough SF₆ continues to be produced to support maintenance of existing infrastructure, expansion of transmission networks and installation of new electrical equipment.

As an auditor, my reaction is always: “Yes, but show me the data.” In this case, the atmosphere itself provides a useful audit, and if the regulations were working, we would not see this uptick, not at this scale. If global demand for SF₆ had entered a sustained decline, we would eventually expect to see that reflected in atmospheric growth rates. Instead, concentrations continue to rise, and recent observations suggest the increase may even be accelerating.

The explanation lies in demand: the world is attempting to decarbonize while simultaneously building more electricity infrastructure than at any point in its history. Renewable energy requires transmission. Electrification requires transmission. Data centers require transmission. Economic development requires transmission. All of those things are entirely rational objectives. They also require switchgear, substations and network assets.

The uncomfortable possibility is that several things can be true at the same time. Leakage rates can be improved. Alternative technologies can gain market share. Regulations can be tightened. And atmospheric concentrations can still rise because the overall system is expanding faster than SF₆ is being removed from it.

The graph and the 2025 uptick do not prove that explanation, but in the absence of hard data on production, the correlation with the recent expansion of solar and generation equipment is unlikely to be coincidental.

To understand why, it is worth putting SF₆ into context. The figures below come from the IPCC Sixth Assessment Report and compare the approximate atmospheric lifetime of several greenhouse gases together with their 100-year Global Warming Potential (GWP).

IPCC Sixth Assessment Report 

Methane is often described as a super pollutant because a relatively small amount can have a disproportionately large climate impact. By that definition, SF₆ certainly qualifies. In fact, it is difficult to avoid the conclusion that SF₆ sits in a category of its own. Methane may be a super pollutant. SF₆ is THE super pollutant.

A kilogram of SF₆ released today has roughly 25,000 times the warming effect of a kilogram of carbon dioxide over a 100-year period. More importantly, it remains in the atmosphere for around 3,200 years. Long after the methane emitted this year has been broken down and removed from the atmosphere, a significant proportion of the SF₆released today will still be present.

That does not mean SF₆ is a larger climate problem than carbon dioxide in absolute terms. The quantities involved are vastly different, and CO₂ remains the dominant driver of climate change. What it does mean is that every tonne matters.

The atmosphere does not care about intentions, policy announcements, or technology roadmaps. It responds to emissions. Looking at the latest NOAA measurements, it is difficult to escape the conclusion that SF₆ deserves a great deal more attention than it currently receives, and when someone talks about electrification, we must include this as part of the carbon cost of doing business.

To learn more, connect with us at clientservices@ecoengineers.us.