Recent drop in emissions from China may speed up ozone layer recovery

Earth — Emissions of a banned CFC fell in 2019

The ozone layer may recover more quickly than first thought, thanks mostly to reduced emissions from China of a banned ozone-depleting gas.

Luke Western at the University of Bristol, UK, and his colleagues analysed data on atmospheric levels of the banned ozone-depleting gas trichlorofluoromethane, or CFC-11, and found that emissions from eastern China declined after 2017. Emissions in 2019 were 10,000 tonnes less than the average annual emissions between 2014 and 2017, says Western.

Another study, led by Steve Montzka at the National Oceanic and Atmospheric Administration in Colorado, which estimated global CFC-11 emissions, also found a decline worldwide in 2019 – a trend that seems to be continuing. “Initial concentration trends in 2020 look similar to those in 2019,” says Montzka.

The decline in CFC-11 emissions from eastern China accounts for around 60 per cent of this recent worldwide decline, says Western.

The hole in the ozone layer above Antarctica has been healing in recent years largely because of the Montreal Protocol agreed internationally in 1987, which banned the production of ozone-depleting substances including CFC-11. But studies in 2018 and 2019 indicated that full recovery of the ozone layer was likely to be delayed, because of illegal production of CFC-11 in China between 2014 and 2017. The reduced emissions from China since 2017 mean this feared delay could now be avoided, say both Montzka and Western.

“If the new emissions had continued at the levels we saw in 2014 to 2017, we could have seen ozone recovery, back to 1980 levels, delayed by a few years,” says Western. “As it stands, we hope that we have avoided any substantial delay to ozone recovery.”

“It’s pleasing to see that the mechanisms of the Montreal Protocol – combining the knowledge of scientists, industry experts, policy makers and national authorities – enabled a rapid and effective response to its first major violation,” says Western.

Craig Poku at the University of Leeds, UK, says the trends displayed in emissions from eastern China are promising but continued monitoring will be critical. “I would say that it’s too early to say that delays in [ozone] recovery will not happen based on the data shown,” he says.

Journal references: Nature, DOI: 10.1038/s41586-021-03277-w and DOI: 10.1038/s41586-021-03260-5

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