Emissions of ozone-killing chemical back in decline, study says

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Emissions of an illegal ozone-killing chemical are back in decline following a surge in recent years, new data suggests.

The substance, trichlorofluoromethane or CFC-11, was banned across the world in 2010 as part of the Montreal Protocol, an international treaty aimed at phasing out chemicals harmful to the ozone layer, which protects people and wildlife from UV radiation.

Global concentrations of CFC-11 – once widely used for making insulating foams for furniture and buildings  – began to decline following the international agreement.

However, in 2018, scientists discovered that the decline in atmospheric CFC-11 levels started to slow after 2013, suggesting an increase in the emissions of the substance from an unknown source, likely in East Asia.

Further investigation by environmental groups and scientists pinned around half of the surge in emissions to factories in eastern China. In response to the findings, Chinese authorities promised to crackdown on the illegal production of CFC-11.

The new study, published in the journal Nature, estimates that global emissions of CFC-11 decreased by around 18,000 metric tons per year from 2018 to 2019.

Study author Professor Martyn Chipperfield, an atmospheric scientist at the University of Leeds, told The Independent: “Since 2018, the emissions of the gas CFC-11 have declined sharply, and are now more in line with what is expected based on the international agreement the Montreal Protocol.

“It is good news for this episode. It seems like this particular CFC-11 issue will not get worse, but some of the CFC-11 produced may be tied up in products and not yet released.

“While this is positive overall, it does show that we need to be vigilant in case there are other contraventions of the Protocol.”

The findings were derived from a global network of stations monitoring changes to levels of chemicals in the atmosphere.

“These are standard observations but they are essential for monitoring what is going on,” said Prof Chipperfield.

“Without them we would not have known about the CFC-11 emission increase in the past.”

A second study, also published in Nature, finds that approximately 60 per cent of the observed decline is the result of reductions in emissions from eastern China after 2017.

Dr Luke Western, co-lead author of the study and an atmospheric scientist from the University of Bristol, said: “The findings are very welcome news and hopefully mark an end to a disturbing period of apparent regulatory breaches.

“If the emissions had stayed at the significantly elevated levels we found, there could have been a delay, possibly of many years, in ozone layer recovery.”