The decline in the atmosphere of an ozone-depleting chemical banned by the Montreal Protocol has recently slowed by half, suggesting a serious contravention of the 196-nation treaty, researchers said on Wednesday.
Measurements at remote sites — including the US government-run Mauna Loa Observatory in Hawaii — of the chemical, known as CFC-11, point to somewhere around China, Mongolia and the Koreas as the source of renewed production.
“We show that the rate of decline of atmospheric CFC-11 was constant from 2002 to 2012, and then slowed by about 50 percent after 2012,” an international team of scientists concluded in a study published in the journal Nature. “This evidence strongly suggests increased CFC-11 emissions from eastern Asia after 2012.”
The chemical can be a byproduct in other chemical manufacturing, but it is supposed to be captured and recycled.
Either someone’s making the banned compound or it is sloppy byproducts that have not been reported as required, said Stephen Montzka, the study’s lead author and a research chemist at the US National Oceanic and Atmospheric Administration. (NOAA)
The ozone layer in the stratosphere, 10km to 40km above Earth’s surface, protects life on the planet from deadly ultraviolet radiation. The 1987 Montreal Protocol banned industrial aerosols such as chlorofluorocarbons (CFCs) that were chemically dissolving ozone, especially above Antarctica.
At its most depleted, around the turn of the 21st century, the ozone layer had declined by about 5 percent. Today, the “hole in the ozone” over the South Pole is showing clear signs of recovery.
“The ozone layer remains on track to recovery by mid-century,” the UN Environment Programme (UNEP) said in a statement, reacting to the findings, adding that “continued increase in global CFC-11 emissions will put that progress at risk.”
The slowdown in reduction of CFC-11 also has implications for the fight against climate change.
“Perhaps even more serious is the role of CFCs as long-lived greenhouse gases,” said Joanna Haigh, a professor at Imperial College London, in commenting on the study.
Two decades ago, CFCs — more potent by far as greenhouse gases than carbon dioxide or methane — accounted for about 10 percent of human-induced global warming.
Widely used in 1970s and 1980s as propellant in aerosol sprays, as well as in refrigeration and air conditioning systems, CFCs do not exist in nature.
“This is the first time that emissions of one of the three most abundant, long-lived CFCs have increased for a sustained period since production controls took effect in the 1980s,” the study concluded.
CFC-11 still contributes about a quarter of all chlorine reaching the stratosphere.
The less rapid decline of CFC-11 could prevent ozone from returning to normal levels, or at least as quickly as hoped, researchers said.
“A timely recovery of the stratospheric ozone layer depends on a sustained decline of CFC-11 concentrations,” they wrote.
Other scientists not involved in the study signaled its importance.
“This is atmospheric detective work at its finest,” said Piers Forester, head of the Priestley International Centre for Climate at the University of Leeds. “The authors pinpoint a new source of CFC-11 to East Asia, breaking Montreal Protocol rules.”
Additional reporting by AP
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