Researchers say that they have pinpointed the major sources of a mysterious recent rise in a dangerous, ozone-destroying chemical.
CFC-11 was primarily used for home insulation but global production was due to be phased out in 2010.
But scientists have seen a big slowdown in the rate of depletion over the past six years.
This new study says this is mostly being caused by new gas production in eastern provinces of China.
CFC-11 is also known as trichlorofluoromethane, and is one of a number of chloroflurocarbon (CFC) chemicals that were initially developed as refrigerants during the 1930s.
However, it took many decades for scientists to discover that when CFCs break down in the atmosphere, they release chlorine atoms that are able to rapidly destroy the ozone layer which protects us from ultraviolet light. A gaping hole in the ozone layer over Antarctica was discovered in the
mid 1980s.
The international community agreed the Montreal Protocol in 1987, which banned most of the offending chemicals. Recent research suggests that the hole in the Northern Hemisphere could be fully fixed by the 2030s and Antarctica by the 2060s.
CFC-11 was the second most abundant CFCs and was initially seen to be declining as expected.
However in 2018 a team of researchers monitoring the atmosphere found that the rate of decline had slowed by about 50% after 2012.
