Comment on egusphere-2023-40

Abstract. Production and consumption of CFC-11 (trichlorofluoromethane, CCl3F), CFC-12 dichlorodifluoromethane, CCl2F2) and CCl4 (carbon tetrachloride) are controlled under the regulations of the Montreal Protocol and have been phased out globally for dispersive use since 2010. Only CCl4 is still widely produced under exemption as a chemical feedstock (non-dispersive use). After 2010, emissions of CFC-11 and CFC-12 should therefore mostly originate from existing banks (e.g. foams and refrigerators), however evidence emerged of an increase in global emissions of CFC-11, which was in part attributed to eastern China. Emissions of CFC-11, CFC-12 and CCl4 have subsequently declined in this region, however the total global increase in CFC-11 was not fully accounted for. The motivation for this work was to assess the emissions of CFC-11 and the associated gases, CFC-12 and CCl4, from Western Europe. All countries in this region have been subject to the controls of the Montreal Protocol since the late 1980s, and, as non-Article-5 Parties, have been prohibited from producing CFCs and CCl4 for dispersive use since 1995. Four different inverse modelling systems are used to estimate emissions of these gases from 2008–2021 using data from four atmospheric measurement stations: Mace Head (Ireland), Jungfraujoch (Switzerland), Monte Cimone (Italy) and Tacolneston (UK). The average of the four model studies found that Western European emissions of CFC-11, CFC-12 and CCl4 between 2008 and 2021 were declining at 3.5 (2.7–4.8) %, 7.7 (6.3–8.0) % and 4.4 (2.6–6.4) % yr−1 respectively. Throughout this period, the highest CFC-11 emissions were in Northern France and Benelux (Belgium, the Netherlands and Luxembourg). Emissions of CFC-12 co-located in this region were slightly higher than elsewhere in Western Europe, and also showed some enhancement of CCl4 emissions. However for CCl4, emissions were highest in the south of France. France had the highest emissions of CFC-11, CFC-12 and CCl4 over the period 2008–2021. Emissions from Western Europe (2008–2021) were on average 2.4 ± 0.4 Gg (CFC-11), 1.3 ± 0.3 Gg (CFC-12), 0.9 ± 0.2 Gg (CCl4). This study concludes that the emissions of CFC-11 from Northern France and Benelux are unlikely to be the result of new production. Our estimated decline in emissions of CFC-11 is consistent with a Western European bank release rate of 3.4 (2.6–4.5) %, which is in the upper half of the published range.

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