"If the emissions were to persist, then we could imagine that healing of the ozone layer, that recovery date, could be delayed by a decade", said Dr Montzka. This led the researchers to posit that someone might be indulging in the production of the chemical.
Emissions of a banned, ozone-depleting chemical are on the rise, a group of scientists reported Wednesday, suggesting someone may be secretly manufacturing the pollutant in violation of an worldwide accord. However, in 1987, an global team of scientists proved that the emissions of such chemicals were actually harming the environment, particularly the ozone layer.
These could hamper the recovery of the ozone hole and worsen climate change.
As a result of the controls, CFC11 concentrations have declined by 15% from peak levels measured in 1993.
Emissions of CFC-11 have climbed 25 percent since 2012, despite the chemical being part of a group of ozone pollutants that were phased out under the 1987 Montreal Protocol.
"Emissions today are about the same as it was almost 20 years ago", he said.
Nearly no CFC-11 has been been produced since 2006 - or so we thought. "We don't know why they might be doing that and if it is being made for some specific goal, or inadvertently as a side product of some other chemical process".
Watson suggested that aircraft flights might be necessary to better identify the source of the emissions.
If the issue is tackled now, the damage will be minor, Montzka says.
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At its most depleted, around the turn of the 21st century, the ozone layer had declined by about five percent.
Exploring further, the researchers found the concentration of CFC-11 to be unusually high in the Northern Hemisphere.
They were also used as propellants in aerosol sprays and in solvents. "Further work is needed to figure out exactly why emissions of CFC11 are increasing, and if something can be done about it soon".
Montzka told the BBC that the data points "fairly definitively" towards Eastern Asia, somewhere around China, Mongolia and the Koreas.
But they concluded these sources could not explain the increase, which they calculated at about 13 billion grams per year in recent years.
CFC-11 still contributes about a quarter of all chlorine - the chemical that triggers the breakdown of ozone - reaching the stratosphere.
If the study is verified, this would be a clear violation of the Montreal Protocol.
"It's disappointing, I would not have expected it to happen", said Dr Michaela Hegglin from Reading University, UK, who was not involved in the study. Some scientists speculate that the substance is likely being produced in East Asia. A new study finds that global CFC-11 emissions are on the rise again, suggesting that production of the banned chemicals continues from an unidentified source. Now, it appears someone is going rogue. If you want more like this, head over to Science As Fact.