Comment on egusphere-2023-3144

Abstract. Hydrofluorocarbons (HFCs) are powerful anthropogenic greenhouse gases (GHGs) with high global warming potentials (GWPs). They have been widely used as refrigerants, insulation foam blowing agents, aerosol propellants, and fire suppression agents. Since the mid-1990s, emissions of HFCs have been increasing rapidly as they are used in many applications to replace ozone depleting chlorofluorocarbons (CFCs) and hydrochlorofluorocarbons (HCFCs) whose consumption and production have been phased out under the Montreal Protocol (MP). Due to the high GWP of HFCs, the Kigali amendment to the MP requires the phase-down of production and consumption of HFCs to gradually achieve an 80–85 % reduction by 2047 starting in 2019 for non-Article 5 (developed) countries with a 10 % reduction against each defined baseline and later schedules for Article 5 (developing) countries. In this study, we have examined long-term high precision measurements of atmospheric abundances of 5 major HFCs (HFC-134a, HFC-143a, HFC-32, HFC-125, and HFC-152a) at Gosan station, Jeju Island, South Korea from 2008 to 2020. Background abundances of HFCs gradually increased, and the inflow of polluted air masses with elevated abundances from surrounding source regions were detected over the entire period. From these pollution events, we inferred regional and country-specific HFC emission estimates using two independent Lagrangian particle dispersion models and Bayesian inversion frameworks (FLEXPART-FLEXINVERT+ and NAME-InTEM). The spatial distribution of the derived “top-down” (measurement based) emissions for all HFCs shows large fluxes from megacities and industrial areas in the region. Our most important finding is that HFC emissions in eastern China and Japan have sharply increased since 2016. The contribution of East Asian HFC emissions to the global total increased from 9 % (2008–2015) to 15 % (2016–2020). In particular, HFCs emissions in Japan (Annex 1 country) rose rapidly from 2016 onward, with accumulated total inferred HFCs emissions being ~76 Gg/yr higher for 2016–2020 than the “bottom-up” (i.e., based on activity data and emission factors) emissions reported to the United Nations Framework Convention on Climate Change (UNFCCC). This is likely related to the increase in domestic demand in Japan for refrigerants and air-conditioning system-related products and incomplete accounting. A downward trend of HFCs emissions that started in 2019 reflects the effectiveness of the F-gas policy in Japan. Eastern China and South Korea, though not obligated to report to UNFCCC, voluntarily reported emissions, which also show differences between top-down and bottom-up emission estimates, demonstrating the need for atmospheric measurements, comprehensive data analysis and accurate reporting for precise emissions management.

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