Comment on egusphere-2023-40

Abstract

<strong class="journal-contentHeaderColor">Abstract.</strong> 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&ndash;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&ndash;4.8) %, 7.7 (6.3&ndash;8.0) % and 4.4 (2.6&ndash;6.4) % yr^&minus;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&ndash;2021. Emissions from Western Europe (2008&ndash;2021) were on average 2.4 &plusmn; 0.4 Gg (CFC-11), 1.3 &plusmn; 0.3 Gg (CFC-12), 0.9 &plusmn; 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&ndash;4.5) %, which is in the upper half of the published range.