Researchers say they have tracked down the root causes of a mysterious rise in a dangerous, ozone-depleting chemical in recent times.
CFC-11 was primarily used for housing insulation, but global production should be discontinued in 2010.
Scientists, however, have noted a sharp slowdown in fatigue over the past six years.
This new study states that this is mainly due to new gas production in the eastern provinces of China.
CFC-11, also known as trichlorofluoromethane, is one of a series of chlorofluorocarbon chemicals (CFCs) originally developed as a refrigerant in the 1930s.
However, it took many decades for scientists to discover this in CFCs. In the atmosphere, they decompose and release chlorine atoms that are able to rapidly destroy the ozone layer that protects us from ultraviolet light. In the mid-1980s, a gaping hole in the ozone layer over the Antarctic was discovered.
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Media Caption 25 years of ice loss in the Antarctic
In 1987, the international community agreed to the Montreal Protocol, which banned most of the disruptive chemicals. Recent research suggests that the hole in the northern hemisphere in the 2030s and in the Antarctic in the 2060s could be completely repaired.
When was the CFC issue discovered? decrease as expected.
In 2018, a research team monitoring the atmosphere found that the rate of decline after 2012 had slowed by about 50%.
This team argued that it would see a new production of the gas from East Asia. The authors of this paper argued that it could delay ozone depletion by a decade if the sources of new production were not shut down.
What did the investigators find there?
Further investigative work in China by the Environmental Investigation Agency in 2018 seemed to indicate that the country was indeed the source. They found that the majority of the polyurethane insulation used the illegal chemical in companies they contacted. The reason was simple: CFC-11 is of better quality and much cheaper than the alternatives.
What does this latest study show?
This new publication seems to confirm unequivocally that about 40-60% of the increase in emissions goes back to East China provinces.
Based on so-called "top-down" measurements of air monitoring stations in South Korea and Japan, the researchers were able to prove that CFC-11 has been increasing since 2012 at production sites in eastern China.
They calculated that emissions from these parts of China would increase by 110% in 2014-2017 compared to the period 2008-2012.
"This new study is based on peak air data coming from China," said lead author Dr. Matt Rigby, a reader at Bristol University, opposite BBC Inside Science.
"Using computer simulations of the transport of these gases through the atmosphere, we can begin to quantify the emissions from different regions, and here we come to that figure of about 7,000 tonnes of additional CFC-11 emissions from China compared to come before 2012.
"However, the data suggest that they are only final releases to the atmosphere. We have no information on how CFC-11 was used or where it was manufactured. It is quite possible that it was made in another region in another part of China, or even in another country, and transported to the place where they manufacture insulation foams. At this point some of it could have been released to the atmosphere.
Where do the remaining emissions come from?
The researchers are not sure, it is possible that the missing emissions come from other parts of China, as the monitoring stations just can not see them, they could also be from India, Africa or
Does this affect climate change?
Yes – the authors say that these CFCs are also very high greenhouse gases, with one ton of CFC-11 equating to around 5,000 Tonnes of CO2.
"Looking at these additional emissions from eastern China, this translates into an emission of about 35 million tonnes of CO2 into the atmosphere, which is equivalent to about 10% of British emissions or comparable to London.
Will China Curb Production?
The Chinese say they have already begun to cut production, as they call it, "rogue manufacturer." Last November, several suspects were arrested in Henan Province, who owned 30 tons of CFC-11.
Clare Perry of the Environmental Investigations Agency (EIA) said the new findings confirmed the need to eradicate production.
"I think there's no doubt in this study that China is the source of these unexpected emissions, and we would hope that China leaves no stone unturned to discover the source of CFC-11 production.
"Until the production of the chemical is discontinued, it is nearly impossible to stop the use and emissions in the foam companies."