Emissions of several banned ozone-destroying chemicals on the increase

The emission of several ozone-destroying chemicals banned by the Montreal Protocol 13 years ago are increasing, researchers have warned. So-called “chlorofluorocarbons”, or CFCs, were widely used in the manufacture of products from aerosol sprays, solvents and refrigerants.

It now seems the release of previously minor CFCs is on the increase as a by-product of the manufacture of ozone-friendly CFC alternatives called hydrofluorocarbons. This CFC release is an exception allowed under the Montreal Protocol, but also contradicts its wider goals.

The study was undertaken by atmospheric scientist Dr Luke Western, of the University of Bristol, and the US National Oceanic and Atmospheric Administration (NOAA)’s Global Monitoring Laboratory and his colleagues.

Dr Western said: “We’re paying attention to these emissions now because of the success of the Montreal Protocol.

“CFC emissions from more widespread uses that are now banned have dropped to such low levels that emissions of CFCs from previously minor sources are more on our radar and under scrutiny.”

According to the researchers, emissions from these sources are not a significant threat to the recovery of the ozone layer — but, as potent greenhouse gases, still have the ability to affect the climate.

Dr Western added: “Combined, their emissions are equal to the CO2 emissions in 2020 for a smaller developed country like Switzerland.

He continued: “That’s equivalent to about one percent of the total greenhouse gas emissions in the United States.”

In their study, the researchers focussed on five CFCs with few, or no, current known uses and that have atmospheric lifetimes ranging from 52–640 years. These compounds are named CFC-13, CFC-112a, CFC-113a, CFC-114a and CFC-115.

In terms of their impact on the ozone layer, their influence was equivalent to around a quarter of that of a recently detected rise in the unreported emissions of CFC-11 — a substance controlled under the Montreal Protocol.

The team analysed measurements from the Advanced Global Atmospheric Gases Experiment (AGAGE), as well as other observations made by the University of East Anglia, NOAA and the Forschungszentrum Jülich in Germany.

These data were combined with an atmospheric transport model, which revealed that global atmospheric abundances and emissions of these CFCs has increased after their production for most uses was phased out in 2010.

According to the researchers, the increased emission of three of the compounds, CFC-113a, CFC-114a and CFC-115, may be partly related to their use in the production of two hydrofluorocarbons employed in air conditioning and refrigeration.

The cause for the increase in the other two CFCs, however, is not known for certain. Furthermore, while the team found rising global emissions of all five compounds, they were unable to pinpoint where they were released.

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Paper co-author and environmental scientist Dr Johannes Laube of the Forschungszentrum Jülich said: “Given the continued rise of these chemicals in the atmosphere, perhaps it is time to think about sharpening the Montreal Protocol a bit more.”

The researchers warned that, if the emissions of the five CFCs continue to rise, their release may work to undo some of the progress achieved by the Montreal Protocol.

However, such emissions might be reduced, the team added, by reducing leakages associated with hydrofluorocarbon production as well as by properly destroying any CFCs produced in such process

Dr Western concluded: “The key takeaway is that the production process for some of the CFC-replacement chemicals may not be entirely ozone-friendly, even if the replacement chemicals themselves are.”

The full findings of the study were published in the journal Nature Geoscience.

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