Although these efforts added clarity to our understanding, uncertainties remain that could hinder effective and rapid mitigation of the unexpected CFC-11 emissions and prevent reliable estimates of the additional damage expected for the ozone layer. If the sharp decline in unexpected global emissions and unreported production is sustained, any associated future ozone depletion is likely to be limited, despite an increase in the CFC-11 bank (the amount of CFC-11 produced, but not yet emitted) by 90 to 725 gigagrams by the beginning of 2020.Īfter the discovery 1 that global emissions and probably also production of the potent ozone-depleting chemical CFC-11 increased after 2012-despite Montreal Protocol controls banning production by 2010-scientists, industry experts, policy makers and others sought information to enable rapid mitigation and to ensure protection of the ozone layer 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12.
The decline in global emissions suggests a substantial decrease in unreported CFC-11 production. We find that global CFC-11 emissions decreased by 18 ± 6 gigagrams per year (26 ± 9 per cent one standard deviation) from 2018 to 2019, to a 2019 value (52 ± 10 gigagrams per year) that is similar to the 2008−2012 mean. Here we report an accelerated decline in the global mean CFC-11 concentration during 20, derived from atmospheric concentration measurements at remote sites around the world. Since 2013, the concentration decline of CFC-11 slowed unexpectedly owing to increasing emissions, probably from unreported production, which, if sustained, would delay the recovery of the stratospheric ozone layer 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12. The atmospheric concentration of trichlorofluoromethane (CFC-11) has been in decline since the production of ozone-depleting substances was phased out under the Montreal Protocol 1, 2. Nature volume 590, pages 428–432 ( 2021) Cite this article A decline in global CFC-11 emissions during 2018−2019
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