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. 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}. Here we report an accelerated decline in the global mean CFC-11 concentration during 2019 and 2020, derived from atmospheric concentration measurements at remote sites around the world. 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. The decline in global emissions suggests a substantial decrease in unreported CFC-11 production. 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.

^{自从根据《蒙特利尔议定书》 1,2}逐步淘汰消耗臭氧层物质的生产以来，三氯氟甲烷 (CFC-11) 的大气浓度一直在下降。自 2013 年以来，CFC-11 的浓度下降出人意料地放缓，原因是排放量增加，可能来自未报告的生产，如果持续下去，将延迟平流层臭氧层的恢复^{1,2,3,4,5,6,7, 8,9,10,11,12}. 在这里，我们报告了 2019 年和 2020 年全球平均 CFC-11 浓度的加速下降，这源于对世界各地偏远地点的大气浓度测量。我们发现，从 2018 年到 2019 年，全球 CFC-11 排放量每年减少 18 ± 6 吉克（26 ± 9%；一个标准偏差），至 2019 年的值（每年 52 ± 10 吉克），与 2008 年相似−2012 平均值。全球排放量的下降表明未报告的 CFC-11 产量大幅下降。如果全球意外排放量和未报告产量的急剧下降持续下去，任何相关的未来臭氧消耗都可能受到限制，尽管 CFC-11 库（生产但尚未排放的 CFC-11 数量）增加了 90到 2020 年初达到 725 千兆克。