27 March 2021

Following the monitoring of the rise and decline in CFC-11 emissions [1], Christina Theodoridi of NRDC [2] commented that “Every year countries submit data on their domestic production of regulated substances. Data reporting is critically important, but it’s not perfect. Collection methods, for example, vary from country to country, and national governments do not always have clear visibility into what happens within their borders. Without atmospheric monitoring, the Montreal Protocol community would be left without a way to check the veracity of this national self-reporting program. The monitoring network is thus vital to the enforcement of the Montreal Protocol and needs to be expanded.” Adding that “According to the new studies, CFC-11 emissions began declining shortly after the international community learned of the problem and turned its attention to solving it. It seems, then, that the international community’s response, plus the domestic actions of the implicated country, were key drivers to bringing illegal emitters into line.”

Atmospheric monitoring can identify trends for emissions of Ozone Depleting Substances that are found in extremely low concentrations (at less than 0.1 ppt, note that 1 part per trillion (ppt) is about the same as 1 cm2 compared to the area of Paris -105.4 sq km). A recent paper reports on “Unexpected nascent atmospheric emissions of three ozone-depleting hydrochlorofluorocarbons”.[3]

Atmospheric modelling is contributing to an ever more detailed understanding of atmospheric concentrations. A recent paper details trends in ocean absorption and emission of CFC-11 as the atmospheric concentration changes. These quantities are relatively small compared to emissions from the bank of CFC-11, in the range 1000 tonnes/year absorption at present changing to emissions of 400 tonnes/year to the atmosphere in 2100. [4]

[1] Emissions of a banned ozone-depleting gas are back on the decline. Discovery in 2018 posed first real test of the Montreal Protocol Emissions of a banned ozone-depleting gas are back on the decline - Welcome to NOAA Research
[2] With CFC-11 Success Comes a Time to Reflect, Christina Theodoridi of NRDC see With CFC-11 Success Comes a Time to Reflect (Pt.II) | NRDC
[3] “Unexpected nascent atmospheric emissions of three ozone-depleting hydrochlorofluorocarbons” PNAS February 2, 2021 118 (5) e2010914118;
[4] On the effects of the oceans on atmospheric CFC-11 lifetimes and emissions, PNAS March 23, 2021 118 (12) e2021528118;

Image: ©Shutterstock/Cefic

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