Staff at the South Pole get ready to release a balloon that will carry an ozone instrument up to 20 miles in the atmosphere, measuring ozone levels all along the.
When a hole in the ozone formed over Antarctica, countries around the world in 1987 agreed to phase out several types of ozone-depleting chemicals called chlorofluorocarbons (CFCs), The Associated Press reported. Use of the chemical was banned in 2010 via the Montreal Protocol, an worldwide agreement made to protect the environment.
Lastly, the team considered whether the new CFC-11 was being produced as a by-product of some other chemical manufacturing process.
The scientists say that the increase is likely a result of new, unreported production of the gas, known as CFC-11, probably in East Asia.
"I've been making these measurements for more than 30 years and this is the most surprising thing I've seen", said Stephen Montzka, a scientist with the National Oceanic and Atmospheric Administration who led the work. "Further work is needed to figure out exactly why emissions of CFC-11 are increasing and if something can be done about it soon".
Widely used in 1970s and 1980s as propellant in aerosol sprays, as well as in refrigeration and air conditioning systems, CFCs do not exist in nature.
"Emissions today are about the same as it was almost 20 years ago", he said. This means that the total concentration of ozone-depleting chemicals, overall, is still decreasing in the atmosphere.
The researchers said that the less rapid decline of CFC-11 could prevent ozone from returning to normal levels, or at least as quickly as hoped. Then, surprisingly, the rate of decline hardly changed over the decade that followed. In 2012, however, the rate of decline suddenly reduced by about 50% - indicating that new source of production had started up.
It is possible that the increased emissions could be due to older buildings being demolished, but that doesn't seem to be the case.
However, if no action is taken on the new source of emissions, it could be highly significant.
There is a small chance that there is a more innocent explanation for the rise in CFC-11 emissions, the scientist say.
Either someone's making the banned compound or it's sloppy byproducts that haven't been reported as required, Montzka said.
But there a growing scientific doubts about the progress of healing in the ozone hole.
"We show that the rate of decline of atmospheric CFC-11 was constant from 2002 to 2012, and then slowed by about 50 percent after 2012", an global team of scientists concluded in a study.
To put that in perspective, production of CFC-11, marketed under the trade name Freon, peaked at about 430,000 tons per year in the 1980s.
Thought the ozone layer was safe?
A study earlier this year found that the ozone layer is unexpectedly declining in the lower stratosphere - 10 to 24 kilometers above sea level - over the planet's populated tropical and mid-latitude regions.
Keith Weller, a spokesman for the United Nations Environment Program, which helps implement the protocol, said the findings would be presented to the parties to the agreement for review.
"It is therefore imperative that this finding be discussed at the next Ministerial meeting of Governments given recovery of the ozone layer is dependent on all countries complying with the Montreal Protocol (and its adjustments and amendments) with emissions globally dropping to zero".