How an Illicit Chemical Is Jeopardizing Recovery of the Ozone Layer

When the Montreal Protocol marked its 30th anniversary in 2017, it seemed like an unalloyed triumph for environmental common sense. By banding together to address a planetary emergency, the 197 signatory nations had officially ended production and use of chemicals responsible for depleting the ozone layer in the upper atmosphere, an essential shield against the sun’s ultraviolet radiation. It was a “milestone for all people and our planet,” according to António Guterres, secretary-general of the United Nations. “The Earth’s Ozone Hole is Shrinking,” one celebratory headline announced. “Without the Ozone Treaty,” another advised, “You’d Get Sunburned in 5 Minutes.”But an unexpected recent spike in emissions of CFCs (or chlorofluorocarbons), the major ozone-depleting chemicals, now suggests it’s far too soon to close the file on ozone depletion. A new study published this week in Nature pins down the source of 7,000 metric tons a year of new CFC-11 (trichlorofluoromethane) emissions to the provinces of Shandong and Hebei on the northeastern coast of China.