Global emissions of several banned ozone-destroying chemicals are increasing

Increased emissions of ozone-depleting chemicals due to loopholes in the Montreal Protocol.


A new study discovered rising emissions of several ozone-depleting chemicals. However, their production is prohibited for most uses under the Montreal Protocol.

The University of Bristol and National Oceanic and Atmospheric Administration (NOAA) research published today in Nature Geoscience puts the rise in part to the chemicals, known as chlorofluorocarbons or CFCs, being used to create other ozone-friendly alternatives to CFCs.

Lead author Dr. Luke Western, a Research Fellow at the University of Bristol and researcher at the NOAA’s Global Monitoring Laboratory (GML), 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.”

The researchers found that ozone recovery is not currently significantly threatened by emissions from these CFCs. However, they still impact the climate because they are strong greenhouse gases.

Western said, “Combined, their emissions are equal to the CO2 emissions in 2020 for a smaller developed country like Switzerland. That’s equivalent to about one percent of the total greenhouse gas emissions in the United States.”

A team of scientists from the United Kingdom, the United States, Switzerland, Australia, and Germany conducted the international study, which focused on five CFCs with few or no known current uses.

CFCs are chemicals known for destroying the Earth’s protective ozone layer. CFCs were once widely used in producing hundreds of products, including aerosol sprays, blowing agents for foams and packing materials, solvents, and refrigeration. However, CFC production for such uses was banned in 2010 under the Montreal Protocol.

However, the international treaty did not prohibit the production of CFCs during the production of other chemicals, such as hydrofluorocarbons or HFCs, which were developed as second-generation replacements for CFCs.

This study focused on five CFCs with few or no known current applications: CFC-13, CFC-112a, CFC-113a, CFC-114a, and CFC-115, with atmospheric lifetimes ranging from 52 to 640 years. In terms of ozone layer impact, these emissions were roughly one-quarter of a recently detected increase in CFC-11 emissions, a substance controlled under the Montreal Protocol that is thought to be due to unreported new production.

This study used measurements from the Advanced Global Atmospheric Gases Experiment (AGAGE), as well as those from Forschungszentrum Jülich in Germany, the University of East Anglia, and NOAA in the United States, 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 discovered that while emissions from these CFCs do not currently pose a significant threat to ozone recovery, they impact the climate.

The researchers determined that the increased emissions from the three CFCs studied may be partly due to their use in the production of two common HFCs used primarily in refrigeration and air conditioning.

The researchers determined that for three CFCs they studied – CFC-113a, CFC-114a, and CFC-115 – the increased emissions may be partly due to their use in producing two common HFCs used primarily in refrigeration and air conditioning.
The reasons for the rising emissions of the other two CFCs, CFC-13 and CFC-112a, are unclear.

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.

The study noted that these emissions might be reduced or avoided by reducing leakages associated with HFC production and properly destroying any co-produced CFCs.

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.”

Journal Reference:

  1. Western, L. M., Vollmer, M. K., etal. Global increase of ozone-depleting chlorofluorocarbons from 2010 to 2020. Nature Geoscience. DOI: 10.1038/s41561-023-01147-w