Those efforts have resulted in an overall 15 per cent decline in the amount of CFC-11 in the atmosphere, according to a 2018 study.
Chlorofluorocarbon-11, or CFC-11, was widely used in the 1970s and 1980s in fridges and air conditioners but was banned along with other industrial aerosols in the 1987 Montreal Protocol because it was found to chemically dissolve the ozone layer, which protects us from ultraviolet light. "The most likely explanation is that new production has taken place before the end of 2017, which is the period covered in our work", said another lead author, Matt Rigby of the University of Bristol.
After the ban came into force, global concentrations of CFC-11 in the atmosphere declined substantially until 2012.More news: Google brings Dark Mode to Calendar | newkerala.com #146122
Industries in north-eastern China have released large quantities of an ozone-depleting gas into the atmosphere in violation of an global treaty, scientists have said.
There were indications that some region in eastern Asia was still emitting thousands of tonnes of CFC-11, but the exact location was not known.
But a report a year ago by the London-based Environmental Investigation Agency (EIA) claimed that dozens of Chinese companies were still using the banned CFC-11 in the production of polyurethane foam.
"We did not find evidence of increased emissions from Japan, the Korean peninsula or any other country", added Luke Western, a post-doctoral researcher at the University of Bristol.More news: Next round of United States tariffs a month away; Mnuchin
The sheer amount of the chemical coming from these regions accounts for up to 60 percent of the global spike in CFC-11 reported past year.
The findings also have implications for the fight against climate change.
The study says the increase in emissions isn't from the pre-Montreal Protocol days because records of the banked amount of CFC-11 in the region were "not large enough to accommodate the emissions that occurred in subsequent years".
Pouring more CFC-11 into the air could also delay ozone levels from returning to normal levels, scientists warn.More news: Westpac tips interest rate cuts in both June and August: Bill Evans
Australian and worldwide investigators believe that a region in northeastern China is producing ozone-layer-destroying chemicals in breach of a global agreement to phase out so-called CFCs.