The global emissions of several banned ozone-depleting chemicals have been increasing, despite being banned for most uses under the Montreal Protocol.
This rise is in part due to the chemicals, known as chlorofluorocarbons, being used to make other ozone-friendly alternatives to CFCs, which is allowed under the Montreal Protocol, but contrary to its wider goals.
CFCs are chemicals known to destroy Earth’s protective ozone layer.
The study — led by the University of Bristol and National Oceanic and Atmospheric Administration and published in Nature Geoscience — found that the emissions from these CFCs currently do not significantly threaten ozone recovery, but they are potent greenhouse gases that still impact the climate.
Researchers discovered that their combined emissions are equal to the CO2 emissions in 2020 for a smaller developed country like Switzerland, which is equivalent to about one per cent of the total greenhouse gas emissions in the US.
The production of CFCs for most uses was banned under the Montreal Protocol in 2010. However, the treaty didn’t eliminate the creation of CFCs during the production of other chemicals, including hydrofluorocarbons, which were developed as second-generation replacements for CFCs.
The study focused on five CFCs with few or no known current uses — CFC-13, CFC-112a, CFC-113a, CFC-114a, and CFC-115 — that have atmospheric lifetimes ranging from 52 to 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.
The international study involved a team of scientists from the UK, US, Switzerland, Australia, and Germany, who used measurements from the Advanced Global Atmospheric Gases Experiment.
They combined these measurements 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.
Researchers found that for three of the CFCs studied — 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.
However, the drivers behind increasing emissions of the other two CFCs, CFC-13 and CFC-112a, are less certain. The researchers were unable to identify particular locations where these rising global emissions originated.
The study suggested that if emissions of these five CFCs continue to rise, their impact may negate some of the benefits gained under the Montreal Protocol.
The authors noted that these emissions might be reduced or avoided by reducing leakages associated with HFC production and by properly destroying any co-produced CFCs.
Dr Luke Western, the lead author of the study, told The National that at present the Montreal Protocol promotes the use of best practices to reduce these emissions.
"We do not know the exact source or mechanism that in which these emissions are released, but it is likely that it is down to leakages during production or improper destruction of byproducts.
"Therefore mitigating these sources would likely help to reduce emissions", Dr Luke Said.
He also cautioned about the harm caused by CFCs in destroying the stratospheric ozone layer. He said: "It can lead to increased levels of skin cancer, cataracts, suppression of the human immune system, and damage to agricultural and ecosystems.
"At current, there has been little impact of stratospheric ozone levels from these CFCs."
The study's co-author, Dr Johannes Laube, from the Institute of Energy and Climate Research at 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.”
Dr Luke Western, the lead author and a research fellow at the University of Bristol and a researcher at the NOAA’s Global Monitoring Laboratory, 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 Montreal Protocol
The Montreal Protocol is an international treaty signed in 1987 to address the depletion of the ozone layer.
It is considered one of the most successful global environmental agreements to date, as it has led to a significant reduction in the production and consumption of ozone-depleting substances, such as CFCs and halons.
Under the treaty, participating countries agreed to phase out the production and consumption of these substances, and to implement measures to protect the ozone layer.
The protocol has been successful in reducing the concentration of these substances in the atmosphere, and the ozone layer is gradually recovering as a result.
However, the recent study has highlighted a loophole in the protocol that allows for the production of CFCs for use in making other ozone-friendly alternatives, which is contributing to increasing emissions of these harmful chemicals.
