In 2016, scientists at MIT and elsewhere observed the first signs of healing in the Antarctic ozone layer. This environmental milestone was the result of decades of concerted effort by nearly every country in the world, which collectively signed on to the Montreal Protocol. These countries pledged to protect the ozone layer by phasing out production of ozone-depleting chlorofluorocarbons, which are also potent greenhouse gases.
While the ozone layer is on a recovery path, scientists have found unexpectedly high emissions of CFC-11 and CFC-12, raising the possibility of production of the banned chemicals that could be in violation of the landmark global treaty. Emissions of CFC-11 even showed an uptick around 2013, which has been traced mainly to a source in eastern China. New data suggest that China has now tamped down on illegal production of the chemical, but emissions of CFC-11 and 12 emission are still larger than expected.
Now MIT researchers have found that much of the current emission of these gases likely stems from large CFC “banks” — old equipment such as building insulation foam, refrigerators and cooling systems, and foam insulation, that was manufactured before the global phaseout of CFCs and is still leaking the gases into the atmosphere. Based on earlier analyses, scientists concluded that CFC banks would be too small to contribute very much to ozone depletion, and so policymakers allowed the banks to remain.
Read more at Massachusetts Institute of Technology
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