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The uncertainty of science: Scientists are baffled by the sudden drop in one kind of atmospheric hydrochlorofluorocarbon (HCFC) gas that is thought to help create the hole in the ozone layer above the south pole.
New measurements show that after a rapid increase of the compound in the atmosphere of the Northern Hemisphere from 0.13 parts per trillion (ppt) in 2000 to 0.50 ppt in 2013, the concentration suddenly dropped to about 0.44 ppt by early 2015. This drop in concentration is equivalent to a 50 percent decline in global emissions percent of the gas: from 3,000 metric tons (3,300 US tons) in 2011 to about 1,500 metric tons (1,700 tons) in 2014, according to the new study.
Now for the kicker: They not only don’t know why this HCFC suddenly declined, they also don’t know where it is coming from. This gas is not one of the gases that were restricted decades ago to save the ozone hole. Until last year, scientists hadn’t even known it existed. And though the article claims it is human-caused, they haven’t yet identified how humans cause it. They hope its sudden decline in the atmosphere will help them pin down its source.