According to a US National Oceanic and Atmospheric Administration (NOAA) study, emissions of Trichlorofluoromethane (CFC-11), one of the chemicals most responsible for the Antarctic ozone hole, is on the rise despite an international treaty, Montreal Protocol, putting an end to its production in 2010.
The study, published in Nature, documents an unexpected hike in the emission of Trichlorofluoromethane, or CFC-11, the second-most abundant ozone-depleting gas in the atmosphere. This gas is a member of the family of chemicals most responsible for the giant hole in the ozone layer that forms over Antarctica each September. CFC chemicals were used in making foams for furniture and buildings, in aerosols and as refrigerants. But they were banned under the global Montreal Protocol after the discovery of the ozone hole over Antarctica in the 1980s.
CFC-11 concentrations declined at an accelerating rate prior to 2002 as expected. Then, the rate of decline hardly changed over the decade that followed. Even more unexpected was that the rate of decline slowed by 50 percent after 2012. However, results from the new analysis of NOAA atmospheric measurements show that from 2014 to 2016, emissions of CFC-11 increased by more than 14,000 tons per year to about 65,000 tons per year, or 25 percent above average emission during 2002 to 2012. 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 conclusion was confirmed by other changes recorded in NOAA measurements during the same period, such as a widening difference between CFC-11 concentrations in the northern and southern hemispheres, showing evidence that the new source was somewhere north of the equator. Measurements from Hawaii indicate the sources of the increasing emissions are likely in eastern Asia. If these emissions continue unabated, they have the potential to slow down the recovery of the ozone layer. It’s, therefore, critical to identify the precise causes of these emissions and take the necessary action.
The Montreal Protocol hailed as the most successful international environmental treaty is a legally binding treaty which has been effective in reducing ozone-depleting gases in the atmosphere and putting controls on the production of most human-produced gases known to destroy ozone. Under the treaty’s requirements, nations have reported less than 500 tons of new CFC-11 production per year since 2010. CFC-11 concentrations have declined by 15 percent from peak levels measured in 1993, as a result.