Global emissions of trichlorofluoromethane (CFC-11) decreased in 2019 to levels close to the average seen from 2008–2012, reports a study in Nature. In a separate paper, approximately 60% of this decline is found to be as a result of reductions in emissions from eastern China after 2017. The findings suggest that the downward trajectory of CFC-11 emissions has been restored and substantial delays in the recovery of the ozone layer may have been avoided.
The Montreal Protocol set out to protect the ozone layer by reducing the abundance of ozone-depleting substances, such as chlorofluorocarbons (CFCs), in the atmosphere. Under the protocol, production of these substances was banned from 2010. However, in 2018 it was reported that the decline in the atmospheric concentration of CFC-11 had slowed since 2013, suggesting an increase in emissions from new, unreported production. Much of this global rise was attributed to emissions from eastern China.
Now, Stephen Montzka and colleagues report observations from two independent global remote measurement networks, which show that since late 2018 the decline in atmospheric CFC-11 has accelerated. The authors found that from 2018 to 2019, global emissions of CFC-11 decreased by approximately 18,000 metric tonnes, resulting in 52,000 metric tonnes of emissions in 2019 (which is comparable to the average emissions from 2008–2012).
In an accompanying paper, Luke Western and colleagues used atmospheric observations from Gosan, South Korea, and Hateruma, Japan, along with chemical transport model simulations, to investigate regional CFC-11 emissions from eastern China. The authors found that emissions have declined in this region by approximately 10,000 metric tonnes per year since 2014–2017 to around 5,000 metric tonnes in 2019. The estimated reduction in emissions accounts for approximately 60% of the global decline over the same period. However, they were unable to determine the sources of the remaining change in emissions.
The authors conclude that rapid mitigation efforts by countries in east Asia and worldwide enabled emissions to decline to pre-2013 levels and, provided these efforts are sustained, delays in the recovery of the ozone layer may have been avoided.
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