A new study reports that worldwide emissions of a potent substance alleged to deplete the Earth’s ozone layer, which is the protective barrier that absorbs the harmful UV rays from the Sun—have decreased very fast and are now again on the decline.
Published recently in the journal Nature, two international studies demonstrate that emissions of CFC-11, one among the various chlorofluorocarbon (CFC) chemicals once extensively used in insulating foams and refrigerators, are again on the decline within two years following the disclosure of their unexpected resurgence caused by suspected illegal production.
The findings are very welcome news and hopefully mark an end to a disturbing period of apparent regulatory breaches. If the emissions had stayed at the significantly elevated levels we found, there could have been a delay, possibly of many years, in ozone layer recovery.
Dr Luke Western, University of Bristol
“On top of that, since CFC-11 is also a potent greenhouse gas, the new emissions were contributing to climate change at levels similar to the carbon dioxide emissions of a megacity,” added Dr Western, who is a co-lead author of one of the studies.
In compliance with the Montreal Protocol, a historic international treaty mandating the phasing-out of ozone-depleting substances, in 2010, the production of CFC-11 was banned worldwide. After that, emissions of CFC-11 should have decreased steadily.
However, in 2018, a few of the same researchers behind the latest more promising discovery identified that there was a spike in emissions starting around 2013. This prompted an alarm at the time the manufacture of the banned substance had resumed in an evident violation of the Montreal Protocol.
The first indications of something unpropitious were identified by an international atmospheric monitoring team headed by the National Oceanic and Atmospheric Administration (NOAA).
We noticed the concentration of CFC-11 had declined more slowly since 2013 than predicted, clearly indicating an upturn in emissions. The results suggested that some of the increase was from eastern Asia.
Dr Steve Montzka, National Oceanic and Atmospheric Administration
Dr Montzka is the lead author of the original research paper. These unpredicted results were verified by the Advanced Global Atmospheric Gases Experiment (AGAGE), an independent global measurement network.
In the words of Professor Ron Prinn from Massachusetts Institute of Technology (MIT), AGAGE principal investigator and co-author of both new papers, “The global data clearly suggested new emissions. The question was where exactly?”
“The answer lay in the measurements at AGAGE and affiliate monitoring stations that detect polluted air from nearby regions. Using data from Korean and Japanese stations, it appeared around half of the increase in global emissions originated from parts of eastern China,” added Professor Prinn.
Further scrutiny by environmental campaigners and media unraveled the use of CFC-11 for producing insulating foams in China. Chinese authorities paid attention, and at the Montreal Protocol meetings in 2018 and 2019, they confirmed certain banned ozone-depleting substances were found as part of factory inspections, but only in minuscule amounts with respect to those inferred from the atmospheric data.
The authorities reported that material seizures, arrests, and the demolition of production facilities were carried out as a result.
The scientific groups have been continuously monitoring atmospheric levels closely, and fresh evidence, published in the two papers on global CFC-11 emissions and eastern Chinese emissions, shows that those efforts have probably led to drastic reductions in emission.
To quantify how emissions have changed at regional scales, we compared the pollution enhancements observed in the Korean and Japanese measurement data to computer models simulating how CFC-11 is transported through the atmosphere. With the global data, we used another type of model that quantified the emissions change required to match the observed global CFC-11 concentration trends.
Matt Rigby, Professor, University of Bristol
“At both scales, the findings were striking; emissions had dropped by thousands of tonnes per year between 2017 and 2019. In fact, we estimate this recent decline is comparable or even greater than the original increase, which is a remarkable turnaround,” added Professor Rigby, who is a co-author of both studies.
Although the study results indicate that the quick action in eastern China and other parts of the world has probably prevented a considerable delay in ozone layer recovery, any undisclosed production will have a lasting impact on the environment.
Professor Rigby added, “Even if the new production associated with the emissions from eastern China, and other regions of the world, has now stopped, it is likely only part of the total CFC-11 that was made has been released to the atmosphere so far. The rest may still be sitting in foams in buildings and appliances and will seep out into the air over the coming decades.”
The estimated eastern Chinese CFC-11 emissions could not be fully attributed to the inferred global emissions, there have been demands to optimize international efforts to monitor and trace any future emitting regions.
According to Professor Ray Weiss, from Scripps Institution of Oceanography, a Principal Investigator in AGAGE, “As a direct result of these findings, the Parties of the Montreal Protocol are now taking steps to identify, locate and quantify any future unexpected emissions of controlled substances by expanding the coverage of atmospheric measurements in key regions of the globe.”
Montzka, S. A., et al. (2020) A decline in global CFC-11 emissions during 2018−2019. Nature. doi.org/10.1038/s41586-021-03260-5.