Numbers Don’t Lie, Do They? On the Gap Between Greenhouse Gas Reports and Reality.

By Hanna Gabriel

Under the Kyoto Protocol, countries must report their greenhouse gas emissions, including one of the most potent greenhouse gases: Sulphur hexafluoride (SF6), used mainly as an insulator in the electrical industry. But the numbers don’t add up. A team of meteorologists has now published both global and regional SF6 emissions, confirming the discrepancies.

Some things only become clear at second glance. Since the 1990s, the “F-gas” sulphur hexafluoride (SF6) has been widely used in various applications. The gas is unreactive, non-flammable, non-toxic, does not contribute to the ozone hole and is a very good insulator – so it seemed logical to use it in everything from the filling of sports shoes and car tyres to double-glazed windows and the electrical industry. But it turns out: SF6 is the greenhouse gas with the worst climate impact.

About a ticking time bomb

“SF6 has 24,300 times the global warming potential of CO2,” says Martin Vojta, a meteorologist at the University of Vienna. “Worse still, it has a lifetime in the atmosphere of about 1,000 years. This means that everything we have emitted so far will stay in the atmosphere, accumulate and warm the climate for hundreds of years.” The EU has therefore limited the use of SF6, and researchers are working on alternative isolation gases or technical solutions to be able to completely avoid using the greenhouse gas.

Vojta is a researcher in the group of Andreas Stohl, Director of the Department of Meteorology and Geophysics at the University of Vienna and a member of the Environment and Climate Research Hub.

“None of the countries’ reported emissions align with the measurements of this greenhouse time bomb.”

In a recent publication, the meteorologists presented the most comprehensive – both temporal and spatial – data to date on SF6 emissions. Their results confirmed a massive gap: None of the countries’ reported emissions align with the measurements of this greenhouse time bomb. In fact, the analysis, based on atmospheric measurements from 2005 to 2021, shows two things: First, countries are massively underestimating their emissions, in some cases by more than half. And second, regional improvements are not enough to reverse the global upward trend in SF6 emissions.

But how does SF6 end up in the atmosphere?

SF6 emissions are usually unplanned. The main source is the high-voltage industry, where the gas is used as an insulator in transformers because of its good electrical properties. It is also used in the semiconductor, aluminium and magnesium industries. In each case, it is unproblematic as long as it remains in the closed system. But if a component fails, leaks or is mishandled during maintenance, the gas is released into the air. This also makes the emissions difficult to determine.

“It was clear that something had to be wrong.”

“Emission reports are based on assumptions. Countries identify where SF6 is being used and then statistically derive the emissions from emission factors, which are often uncertain,” explains Vojta. In addition, data may be missing or SF6 sources may be overlooked. And, of course, illegal emissions are not accounted for. These reports are entered into a public registry maintained by the UNFCCC (United Nations Framework Convention on Climate Change) Secretariat. “In the case of SF6, previous work has shown that the sum of reported emissions is much lower than global SF6 concentration measurements demonstrate,” says Vojta. “It was clear that something had to be wrong.”

A detective’s approach: retracing emissions

“The uniqueness of our study is that we have determined global and regional emissions at the same time.”

In their own work, the researchers took a different route to arrive at their figures. Instead of statistical extrapolations, they used atmospheric measurements from monitoring stations all over the world – for example in South Korea, Barbados and Tenerife – and modelled them back to their respective emission sites. “The air arriving at the monitoring station is traced back over 50 days. That way, we can say where the emissions are coming from and how big the emissions are from a particular region,” says Vojta. In short, they calculate how high the emission at a specific location must have been to explain the measurements – a well-established method called inverse modelling.

“The uniqueness of our study is that we have determined global and regional emissions at the same time. This allows us to look specifically at countries with high emissions, such as the US, Europe and China, but also to check whether these are consistent with global emissions. This is important because in many regions of the world we know very little about the SF6 emissions,” says Vojta.

Regulations are effective and needed

The researchers found that in the US, SF6 emissions fell sharply from 1.25 gigagrams (Gg) in 2005 to 0.48 Gg in 2021. However, this was still double the emissions reported to the United Nations. In the EU, SF6 emissions also show a downward trend of -0.006 Gg/year, including a significant drop in 2018, which the researchers interpret as an important indication of the impact of new EU regulations. In contrast to both the EU and the US, China’s emissions quadrupled from 1.28 Gg in 2005 to 5.16 Gg in 2021. This makes China’s increase even greater than the global trend.

“National reports for the US, Europe and China all underestimated their SF6 emissions,” the authors conclude in their paper showcasing the weaknesses of extrapolations as compared to actual measurements. But they did see some positive developments. For example, the 2018 drop found in EU SF6 emissions is most likely due to the EU’s implementation of the F-gas regulation in 2014. “With these results, we can really show that the regulations are having an effect. This speaks for the success of the F-gas regulation and is politically important,” says Stohl.

“The problem now lies elsewhere”

As a reform of the 2014 regulation, the EU further restricted the use of SF6 in March this year, a milestone towards climate-neutrality. But as with many things related to climate change, a regional solution is not enough. “The problem now lies elsewhere,” says Stohl, pointing out that the emissions in Europe or the US are about a tenth of those in China. “Strict regulations in East Asian countries, such as China, would be a great success,” adds Vojta.

Thorough monitoring as a primary goal 

The immense climate impact of SF6 has been known for some time, and efforts have been made in some countries to bring emissions under control. “This has been successful regionally, but globally emissions continue to rise,” says Stohl, who fears that regulations in one country could lead to rising emissions in another, for example in the case of China and India. 

But research and measurements in these regions are limited by a very practical problem: many countries are not covered by monitoring stations. Both Stohl and Vojta agree that more needs to be done to ensure better monitoring in these regions. This would allow common statistical reports to be combined with atmospheric measurements. Perhaps then the numbers will finally add up. 

• Sulphur hexafluoride (SF6) is widely used in various industries. However, it is the most potent greenhouse gas, with a global warming potential 24,300 times greater than CO2.
• Countries are massively underestimating their SF6 emissions, with some countries reporting figures that are less than half of the actual emissions.

• Regional efforts – though useful – are not sufficient to reverse the globally rising trend of SF6 emissions.

• More extensive monitoring and measurement, especially in the Global South and populous countries like India, is crucial for obtaining accurate data and better understand and control SF6 emissions globally.

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