Factories in northeastern China have produced large amounts of ozone-depleting gas, CFC-11, in violation of an international treaty, according to a study in Nature .
Since 2013, annual emissions of this gas have increased by about 7,000 tons, according to scientists who conducted this study released Wednesday. "Chlorofluorocarbons (CFCs) are the main contributors to the depletion of the stratospheric ozone layer, which protects us from the sun's ultra-violet radiation," said lead author Matt Rigby of Bristol University.
China says it halted production of CFCs in 2007
In 1987, an international agreement, the Montreal Protocol, was signed to phase out CFCs (used in refrigeration and aerosols), responsible for the famous "hole" in this gaseous layer - especially over Antarctica and Australia - protecting the Earth from rays that cause skin cancer, eye and immune damage. In accordance with the Montreal Protocol, the production of CFCs officially ended in 2010 in developing countries. China for its part claims to have ended in 2007.
This ban had led to a significant decrease in overall CFC-11 levels through 2012. But scientists discovered last year that the rate of decline had halved between 2013 and 2017, meaning that had occurred.
CFC-11 can persist in the atmosphere for about fifty years
The Environmental Investigation Agency (EIA), an environmental association based in the United States, pointed in July 2018 in a report 18 factories in 10 provinces of China that agreed to continue using CFCs. To go further, an international team of scientists has collected additional data from measurement stations in Japan, South Korea and Taiwan. "Our measurements showed 'peaks' of pollution when air comes from China's industrialized areas," says another lead author of the study, Sunyoung Park of Kyungpook National University.
Computer simulations have confirmed the origin of these CFC-11 molecules. "We have not found evidence of increased emissions from Japan, the Korean peninsula or other countries," said Luke Western of Bristol University. CFC-11 is also a very powerful greenhouse gas, which can persist in the atmosphere for about fifty years.