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Chemicals banned from air conditioners and refrigerators are making a comeback — and scientists don’t know why

Chemicals banned from air conditioners and refrigerators are making a comeback — and scientists don’t know why


These chemicals create holes in the ozone layer and are powerful greenhouse gases. They’ve been banned since 2010, but pollution has kept growing.

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A rendering of the Earth with a huge blue patch over Antarctica.
In this image from September 2006, the Antarctic ozone hole measured 11.4 million square miles (29.5 million square kilometers).
Image: Universal History Archive/ Universal Images Group via Getty Images

Chemicals that were banned after they punched a hole in Earth’s ozone layer are still building up at an alarming rate in our atmosphere, according to research published today in the journal Nature Geoscience. The chemicals were once widely used in air conditioning and refrigeration but were supposed to be phased out globally by 2010.

Scientists were surprised to find that concentrations of several types of those chemicals have climbed since then, reaching a record high in 2020. The culprit could be alternative refrigerants that were meant to replace the ozone-depleting substances, the new research suggests. An even bigger problem? Researchers can’t find where all the chemicals are leaking from.

The ozone layer has managed to make a remarkable recovery over the past few decades. If emissions continue to climb, however, it could counteract some of that progress and exacerbate climate change.

“It’s just the sheer size of it.”

“Emissions of these few gases are at the same level as the emissions of all greenhouse gases in Switzerland,” Stefan Reimann, a researcher from Empa, the Swiss Federal Laboratories for Materials Science and Technology, said in a March 30th press briefing. “Being from Switzerland that’s really something which boggles me.”

Reimann and his colleagues spotted rising emissions of five different types of chlorofluorocarbons, or CFCs. Aside from being widely used in refrigerants, CFCs were also ubiquitous in aerosol sprays, foam packaging, and insulation. There are many different kinds of CFCs, all of which were supposed to be phased out worldwide by 2010 under the Montreal Protocol.

The Montreal Protocol, the global deal brokered to repair the ozone layer, has largely been seen as a monumental success. It was adopted soon after researchers discovered a gaping hole in the ozone layer over Antarctica in the 1980s. The protocol forced manufacturers to find alternatives to CFCs and other ozone-depleting substances. Thanks to that, Earth’s ozone layer is on the mend — which lowers the risk of people developing skin cancer and cataracts. Researchers expect the ozone layer to resemble its old self — before the Antarctic hole — around 2066.

That’s why the discovery of rising CFC emissions is such a curveball. CFCs have been gradually phased out since the Montreal Protocol was adopted in 1987. At the very least, emissions should have dropped since production and consumption of the chemicals was completely banned in 2010.

The new research suggests that a loophole in the Montreal Protocol has allowed certain kinds of CFCs to proliferate. While CFCs are supposed to be virtually nonexistent in products that used to contain them, companies are technically still allowed to use CFCs in the process of manufacturing alternatives. In other words, CFCs can be used as feedstock, or ingredients used to make a new chemical.

That’s the case for three of the five CFCs that have become more prevalent since 2010 (CFC-113a, CFC-114a, and CFC-115). They’re used to make hydrofluorocarbons, or HFCs, that replaced CFCs in air conditioning, refrigerators, and fire extinguishers.

Unfortunately, HFCs are also problematic when they leak from appliances. They’re “super” greenhouse gases that are hundreds to thousands of times more potent than carbon dioxide when it comes to their ability to heat the planet. Basically, policymakers created a new problem by trying to solve an old one. So now, the use of HFCs globally is supposed to drop by 85 percent by 2047 under the 2016 Kigali Amendment to the Montreal Protocol.

Companies are supposed to be able to contain leaks and destroy any remaining CFCs that result from the manufacturing of HFCs or other chemicals. But that might not be happening, the new research suggests, since these CFC emissions are rising.

Scientists can’t see exactly what’s causing that rise in pollution, in part because there isn’t robust monitoring across the globe. The authors of the new study measured CFCs from 14 sites around the world.

“We don’t really know where it’s coming from and that’s really a bit scary.”

“You can think of it like if you lost your keys in a field of grass and you only could go to 10 or 15 specific points to look for your keys,” Isaac Vimont, a research scientist at the National Oceanic and Atmospheric Administration’s Global Monitoring Laboratory, said during the press briefing. “If you happen to be right next to your keys, you’ll see them very easily. But if you aren’t, and you can’t go to any other place in that field, except those specific points, it’s much harder to figure out where they are.”

For that reason, the researchers are even more in the dark about what’s causing the rise in emissions of two kinds of CFCs (CFC-13 and CFC-112a) that aren’t even used in the production of HFCs. “We don’t really know where it’s coming from and that’s really a bit scary,” Reimann said in the press briefing.

Fortunately, for now, pollution from the five evasive types of CFCs studied in the new paper isn’t enough to counteract decades of work to eliminate the majority of ozone-depleting substances. But if those emissions become a bigger problem, they could delay some of that recovery, the research warns. And the pollution could contribute to new threats posed by climate change.

Careful monitoring and enforcement of the Montreal Protocol, however, could go a long way toward protecting the planet from that pollution. “Eradicating these emissions is an easy win,” Luke Western, a research fellow at NOAA and the University of Bristol, said during the press briefing.