Industries in northeastern China have spewed large quantities of an ozone-depleting gas into the atmosphere in violation of an international treaty, scientists said Wednesday.
Since 2013, annual emissions from northeastern China of the banned chemical CFC-11 have increased by about 7,000 tonnes, they reported in the peer-reviewed journal Nature.
“CFCs are the main culprit in depletion of the stratospheric ozone layer, which protects us from the Sun’s ultra-violet radiation,” said lead author Matt Rigby, an atmospheric chemist at the University of Bristol.
Chlorofluorocarbon-11 was widely used in the 1970s and 1980s as a refrigerant and to make foam insulation.
The 1987 Montreal Protocol banned CFCs and other industrial aerosols that chemically dissolve protective ozone 10-to-40 kilometres (6-25 miles) above Earth’s surface, especially over Antarctica and Australia.
Following the ban’s entry into force, global concentrations of CFC-11 declined steadily until about 2012.
But last year startled scientists discovered that the pace of that slowdown dropped by half from 2013 to 2017. Because the chemical does not occur in Nature, the change could only have been produced by new emissions.
Evidence pointed to East Asia, but could not nail down the exact origin.
“Our monitoring stations were set up in remote locations far from potential sources,” explained co-author Ron Prinn, a professor at MIT.
Reports last year from the Environmental Investigation Agency fingered Chinese foam factories in the coastal province of Shandong and the inland province of Hebei, which surrounds Beijing.
Suspicions were strengthened when authorities subsequently shut down some of these facilities without explanation.