...Between 2002 and 2012, CFC-11 emissions averaged 54,000 tonnes per year, owing to gradual leakage of old stores of the compound contained in foam insulation and appliances made before the mid 1990s. But the researchers found that between 2014 and 2016, average emissions grew to 67,000 tonnes a year — an increase of roughly 25%1. They also noted that, in 2013, the flask data at the Mauna Loa Observatory in Hawaii suddenly showed increased levels of CFC-11 in the pollution plumes regularly recorded at the site. On closer investigation, they found that the sources of those plumes, and the uptick in CFC-11 emissions, came from eastern Asia.
A team of scientists immediately began to look for clues in an independent set of measurements, in particular those from the AGAGE stations on Jeju Island in South Korea, and Hateruma in Japan. Data from these stations revealed spikes in CFC-11 whenever plumes of pollution passed by. And the spikes had grown since 2013.
With this information, the scientists ran computer models using atmospheric circulation data and the monitoring-station measurements to determine where the pollution was coming from. Four independent modelling groups worked on solving the puzzle, and all came back with the same answer: about 7,000 tonnes per year were coming from the Chinese provinces of Shandong and Hebei...I think it's pretty cool that they were able to detect this with some gas chromatographs. Read the whole thing.