Scientists Baffled By Unknown Source of Ozone-Depleting Chemical

Scientists have found that, despite a complete ban since 2007, ozone-depleting chemicals are still being pumped into the atmosphere from some unknown source. "Carbon tetrachloride (CCl4), which was once used in applications such as dry cleaning and as a fire-extinguishing agent, was regulated in 1987 under the Montreal Protocol along with other chlorofluorocarbons that destroy ozone and contribute to the ozone hole over Antarctica. Parties to the Montreal Protocol reported zero new CCl4 emissions between 2007-2012. However, the new research shows worldwide emissions of CCl4 average 39 kilotons (about 43,000 U.S. tons) per year, approximately 30 percent of peak emissions prior to the international treaty going into effect. "We are not supposed to be seeing this at all," said Qing Liang, an atmospheric scientist at NASA's Goddard Space Flight Center in Greenbelt, Maryland, and lead author of the study published online in the Aug. 18 issue of Geophysical Research Letters, a journal of the American Geophysical Union. "It is now apparent there are either unidentified industrial leakages, large emissions from contaminated sites, or unknown CCl4 sources."

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