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Trichlorofluoromethane, or CFC-11, is the second-most abundant ozone-depleting gas in the atmosphere and a member of the family of chemicals most responsible for the giant hole in the ozone layer that forms over Antarctica each September. Once widely used as a foaming agent, production of CFC-11 was phased out by the Montreal Protocol in 2010.
The new study, published today in Nature, documents an unexpected increase in emissions of this gas, likely from new, unreported production.
Flag - Community - Recovery - Ozone - Depletion
"We're raising a flag to the global community to say, 'This is what's going on, and it is taking us away from timely recovery from ozone depletion,'" said NOAA scientist Stephen Montzka, lead author of the paper, which has co-authors from CIRES, the UK, and the Netherlands. "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. A smaller amount of CFC-11 also exists today in chillers.
CFC-11 - One-quarter - Present - Today - Stratosphere
Because CFC-11 still accounts for one-quarter of all chlorine present in today's stratosphere, expectations for the ozone hole to heal by mid-century depend on an accelerating decline of CFC-11 in the atmosphere as its emissions diminish -- which should happen with no new CFC-11 production.
Despite the increase in CFC-11 emissions, its concentration in the atmosphere continues to decrease, but only about half as fast as the decline observed a few years ago, and at a substantially slower rate than expected. This means that the total concentration of ozone-depleting chemicals, overall, is still decreasing...
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