Western European emission estimates of CFC-11, CFC-12 and CCl ₄ derived from atmospheric measurements from 2008 to 2021

Production and consumption of CFC-11 (trichlorofluoromethane, CClinline-formula₃F), CFC-12 (dichlorodifluoromethane, CClinline-formula₂Finline-formula₂) and CClinline-formula₄ (carbon tetrachloride) are controlled under the regulations of the Montreal Protocol and have been phased out globally since 2010. Only CClinline-formula₄ is still widely produced as a chemical feedstock. After 2010, emissions of CFC-11 and CFC-12 should therefore mostly originate from existing banks (e.g. from foams, mobile air conditioning units and refrigerators); however evidence has emerged of an increase in global emissions of CFC-11 in the last decade, some of which has not been fully accounted for. The motivation for this work was to assess the emissions of CFC-11, CFC-12 and CClinline-formula₄ 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 CClinline-formula₄ for dispersive use since 1996. Four different inverse modelling systems are used to estimate emissions of these gases from 2008 to 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 CClinline-formula₄ between 2008 and 2021 were declining at 3.5 % yrinline-formula⁻¹ (2.7 % yrinline-formula⁻¹–4.8 % yrinline-formula⁻¹), 7.7 % yrinline-formula⁻¹ (6.3 % yrinline-formula⁻¹–8.0 % yrinline-formula⁻¹) and 4.4 % yrinline-formula⁻¹ (2.6 % yrinline-formula⁻¹–6.4 % yrinline-formula⁻¹), respectively. Even though the emissions were declining throughout the period, the area including northern France, Belgium, the Netherlands and Luxembourg showed consistently elevated emissions of CFC-11 compared with the surrounding regions. Emissions of CFC-12 were slightly elevated in the same region. CClinline-formula₄ emissions were the highest in the south of France. France had the highest emissions of all three gases over the period 2008–2021. Emissions from western Europe (2008–2021) were on average 2.4 inline-formula± 0.4 Gg (CFC-11), 1.3 inline-formula± 0.3 Gg (CFC-12) and 0.9 inline-formula± 0.2 Gg (CClinline-formula₄). Our estimated decline in emissions of CFC-11 is consistent with a western European bank release rate of 3.4 % (2.6 %–4.5 %). This study concludes that emissions of CFC-11, CFC-12 and CClinline-formula₄ have all declined from 2008 to 2021 in westernpage7384 Europe. Therefore, no evidence is found that western European emissions contributed to the unexplained part of the global increase in atmospheric concentrations of CFC-11 observed in the last decade.