Emissions of one of the chemicals most responsible for the Antarctic ozone hole are on the rise, despite an global treaty that required an end to its production in 2010, a new NOAA study shows. "Further work is needed to figure out exactly why emissions of CFC-11 are increasing and if something can be done about it soon".
CFCs were once widely used in the manufacture of aerosol sprays, as blowing agents for foams and packing materials, as solvents, and as refrigerants. Though production of CFCs was phased out by the Montreal Protocol, a large reservoir of CFC-11 exists today primarily contained in foam insulation in buildings, and appliances manufactured before the mid-1990s.
The findings, published in the journal Nature, show that since 2012, the rate of decline for a substance known as CFC-11 has slowed, and Montzka's research suggests new emission sources may have popped up over East Asia. Production was banned, emissions fell and the hole slowly shrank. After considering a number of possible causes, Montzka and his colleagues concluded that CFC emissions must have increased after 2012.
"Any production of an ozone-depleting gas that's controlled by the Montreal Protocol has to be reported to the ozone secretariat, and, currently, global production is essentially zero".
The researchers are puzzled as to what the motivation for any unauthorised new production might be. This conclusion was confirmed by other changes recorded in NOAA's measurements during the same period, such as a widening difference between CFC-11 concentrations in the northern and southern hemispheres - evidence that the new source was somewhere north of the equator.
The study authors point out that while CFC-11 can persist in the atmosphere for 50 years, the overall level of chlorine atoms is still declining.
That has led scientists to predict that by mid- to late-century, the abundance of ozone-depleting gases would to fall to levels last seen before the Antarctic ozone hole began to appear in the early 1980s.
"The newer substances that are out there, the replacements for CFC-11, might be more hard or expensive for some countries to produce or get at". Emissions of this CFC to the atmosphere reached about 386,000 tons per year at their peak later in the decade. "But this is most surprising one".
"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.
David Doniger, director of the climate and clean energy program of the Natural Resources Defense Council, an environmental group in Washington, said the new emissions were "bad for the ozone layer and bad for climate change".
But Mr. Doniger noted that the Montreal Protocol, which has been signed by almost 200 countries, has a strong track record of compliance, with countries often reporting their own violations.