How are global emissions of banned CFCs increasing?

International researchers have found increasing emissions of several ozone-depleting chemicals, despite their production being banned for most uses under the Montreal Protocol — and a loophole in the rules is likely responsible.

Chlorofluorocarbons, or CFCs, are chemicals known to destroy Earth’s protective ozone layer. Once widely used in the manufacture of hundreds of products including aerosol sprays, CFC production for such uses was banned under the Montreal Protocol in 2010. However, the international treaty didn’t eliminate the creation of CFCs during production of other chemicals including hydrofluorocarbons (HFCs), which were developed as ozone-friendly replacements for CFCs.

The new study focused on five CFCs with few or no known current uses — CFC-13, CFC-112a, CFC-113a, CFC-114a and CFC-115 — and that have atmospheric lifetimes ranging from 52–640 years. In terms of their impact on the ozone layer, these emissions were equivalent to around one-quarter of a recently detected rise in emissions of CFC-11, a substance controlled under the Montreal Protocol, thought to be due to unreported new production.

The researchers used measurements from the Advanced Global Atmospheric Gases Experiment (AGAGE), in which the University of Bristol plays a pivotal role, as well as others made by Germany’s Forschungszentrum Jülich, the University of East Anglia and the US National Oceanic and Atmospheric Administration (NOAA). These were combined with an atmospheric transport model to show that global atmospheric abundances and emissions of these CFCs increased after their production for most uses was phased out in 2010.

The researchers determined that for CFC-113a, CFC-114a and CFC-115, the increased emissions may be partly due to their use in the production of two common HFCs used primarily in refrigeration and air conditioning. The drivers behind increasing emissions of CFC-13 and CFC-112a are less certain. The results were published in the journal Nature Geoscience.

Emissions from these CFCs currently do not significantly threaten ozone recovery, the researchers noted — but because they’re potent greenhouse gases, they still affect the climate. According to lead author Dr Luke Western, a research fellow at the University of Bristol and researcher at NOAA, “Combined, their emissions are equal to the CO₂ emissions in 2020 for a smaller developed country like Switzerland. That’s equivalent to about 1% of the total greenhouse gas emissions in the United States.”

According to the researchers, if emissions of these five CFCs continue to rise, their impact may negate some of the benefits gained under the Montreal Protocol. These emissions might be reduced or avoided by reducing leakages associated with HFC production and by properly destroying any co-produced CFCs.

“Given the continued rise of these chemicals in the atmosphere, perhaps it is time to think about sharpening the Montreal Protocol a bit more,” concluded study co-author Dr Johannes Laube, from Forschungszentrum Jülich.

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