"This is the most surprising and unexpected thing that I've observed in 27 years of making these measurements", said Steve Montzka, a research chemist at NOAA and lead author of the paper.
The most likely source, according to the study, is from new, unreported production from an unidentified source in East Asia.
Given that the boost in output will inevitably slow the planet's ozone layer recovery, discovering the source of the new production would seem an urgent priority. Then, surprisingly, the rate of decline hardly changed over the decade that followed. After considering a number of possible causes, Montzka and his colleagues concluded that CFC emissions must have increased after 2012. More work will be needed to narrow down the locations of these new emissions, Montzka said.
An ozone depleting CFC refrigerant, thought to be virtually extinct following Montreal Protocol phase outs, has mysteriously reappeared in increasing amounts in the atmosphere. Under the treaty's requirements, nations have reported less than 500 tons of new CFC-11 production per year since 2010.
As a result of the controls, CFC11 concentrations have declined by 15% from peak levels measured in 1993.
Image The largest ever spotted ozone hole over Antarctica. Pic NASA
Something odd is happening with a now-banned chemical that eats away at Earth's protective ozone layer: Scientists say there's more of it - not less - going into the atmosphere and they don't know where it is coming from.
The findings of Montzka and his team of researchers from the Cooperative Institute for Research in Environmental Sciences (CIRES), the United Kingdom, and the Netherlands, represent the first time that emissions of one of the three most abundant, long-lived CFCs have increased for a sustained period since production controls took effect in the late 1980s. If not remedied soon, however, substantial delays in ozone layer recovery could be expected, Montzka said.
If the source of these emissions can be identified and mitigated soon, the damage to the ozone layer should be minor.
The Montreal Protocol, signed by more than 200 countries and generally regarded as having a good record of compliance, is created to protect the Earth's ozone layer.