Four ozone-depleting substances discovered

ozone hole over Antarctica on September 12, 2011 / NASA Earth Observatory
Janet Fang 10 Mar 2014, 22:17
 
The story of chlorofluorocarbons (CFCs) is mostly thought of as a global success. These manmade substances used to be common in household items, from refrigerants to hairsprays. But when evidence came out in 1985 showing how they were causing a hole in the UV-blocking ozone layer over Antarctica, laws to reduce and ultimately phase out CFCs came into force in the late 1980s, with a total global ban in 2010. The ozone layer was set to recover by 2050.  
 
Scientists have now detected four new ozone-depleting substances that started to emerge in the atmosphere in the 1960s. 
 
A team led by Johannes Laube from the University of East Anglia compared the composition of today’s air with two other sources: air samples collected from unpolluted Tasmania between 1978 and 2012 and gas extracted from deep-compacted snow in Greenland. The latter, called polar firn, provides a century-old archive of the atmosphere. 
 
They identified three new CFC compounds and one new hydrochlorofluorocarbon compound in the air samples (HCFCs were used to replace CFCs, though they still cause damage). About 74,000 metric tons have been released so far. 
 
What’s particularly worrisome: “We don’t know where the new gases are being emitted from,” Laube says in a news release. They also don’t know if the emissions were illegal, given exemptions and loopholes in the Montreal Protocol of 1987, he tells Reuters. Possible sources include agricultural insecticides and solvents for cleaning electronic parts. 
 
All four compounds started to appear in the atmosphere in the 1960s, suggesting they are manmade, and two of them have been increasing in concentration ever since -- the likes of which we haven’t seen since the international treaty went into effect. Although according to experts, the concentrations are considered “tiny” and not yet a threat to the ozone layer; during peak emissions in the 1980s, we saw a million metric tons a year. However, even if we nix their emissions immediately, they’ll still be hanging around for decades to come. 
 
“This paper highlights that ozone depletion is not yet yesterday’s story,” says Piers Forster from the University of Leeds. “We need to be vigilant and continually monitor the atmosphere for even small amounts of these gases creeping up, either through accidental or unplanned emissions.”
 
The work was published in Nature Geoscience on Sunday. 
 
Image: ozone hole over Antarctica / NASA Earth Observatory
 
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