Who is destroying the ozone layer? In recent decades, concentrations of chlorofluorocarbon gases have been declining in the atmosphere, which is good news for the ozone layer鈥檚 recovery and action on climate change.
But levels of the second most abundant of those gases, trichlorofluoromethane (CFC-11), have been rising since 2013, .
The culprit appears to be illegal production of CFCs in eastern China, in defiance of a 2010 ban on their manufacture.
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An international team traced the source of the spikes in the pollutant back from two monitoring stations, one in Japan and one in South Korea. They were the only ones in the world which saw such events.
To pinpoint which country was responsible, the team used models to simulate how the atmosphere would distribute the plumes. The results pointed clearly to the Chinese provinces of Shandong and Hebei. 鈥淲e think the rise from this region explains the increase in CFCs,鈥� says Matt Rigby of the University of Bristol.
Globally, around 65,000 tonnes of CFCs leak into the atmosphere each year from existing buildings and refrigerators. The new research suggests China is responsible for 40-60 per cent of the previously unexplained rise in CFCs. China appears to have been emitting 10,000 tonnes a year between 2013 and 2017, more than doubling the country鈥檚 previous contribution.
An investigation by the Environmental Investigation Agency (EIA) last year found clues the culprit in China was small factories buying CFC-11 to make foam insulation for fridges, because it was cheaper than its legal alternative, HCFC-141b.
Rigby鈥檚 study provides definitive evidence of what the EIA had hinted was the answer, and sheds more light on the scale of the problem. 鈥淭he [EIA] investigation clearly showed foam manufacturers were using this compound but it鈥檚 very difficult from that information to see how significant that usage was on the global scale we鈥檝e seen,鈥� he says.聽鈥淲hat we鈥檝e shown is exactly what鈥檚 made it into the atmosphere.鈥�
There are signs the Chinese authorities are taking the issue seriously, with . But the latest available data, to the end of 2018, shows no slowdown in the CFC-11 emissions from China.
The UN Environment Programme said the CFC-11 issue was a priority. Joyce Msuya, the group鈥檚 acting head, says: 鈥淎ction is being taken by all parties at the international level and by China domestically.鈥�
If the problem continues unchecked, it poses serious risks for the recovery of the ozone layer as well as an unwanted extra fuel for global warming.
鈥淭he extra emissions we鈥檝e seen over the last 4-5 years, if they stopped tomorrow it shouldn鈥檛 delay ozone recovery substantially,鈥� says Rigby. 鈥淏ut if they continue, we could see delays of several years, even decades.鈥�
Steve聽Montzka of the US聽National Oceanic and Atmospheric Administration said the research was significant but there are still unanswered questions, in particular where the other half of the recent rise in CFC-11 is coming from.
Journal reference: Nature,
