Recent increases in the atmospheric growth rate and emissions of HFC-23 (CHF3) and the link to HCFC-22 (CHClF2) production. 2

摘要: High frequency measurements of trifluoromethane (HFC-23, CHF3), a potent hydrofluorocarbon 25 greenhouse gas, largely emitted to the atmosphere as by-product of production of the 26 hydrochlorofluorocarbon HCFC-22 (CHClF2), at five core stations of the Advanced Global 27 Atmospheric Gases Experiment (AGAGE) network, combined with measurements on firn air, 28 old Northern Hemisphere air samples and Cape Grim Air Archive (CGAA) air samples, are used 29 to explore the current and historic changes in the atmospheric abundance of HFC-23. These 30 measurements are used in combination with the AGAGE 2-D atmospheric 12-box model and a 31 Bayesian inversion methodology to determine model atmospheric mole fractions and the history 32 of global HFC-23 emissions. The global modelled annual mole fraction of HFC-23 in the 33 background atmosphere was 28.9±0.6 pmol mol-1 at the end of 2016, representing a 28% 34 increase from 22.6±0.4 pmol mol-1 in 2009. Over the same time frame, the modelled mole 35 fraction of HCFC-22 increased by 19% from 199±2 pmol mol-1 to 237±2 pmol mol-1. 36 However, unlike HFC-23, the annual average HCFC-22 growth rate slowed from 2009 to 2016 37 at an annual average rate of-0.5 pmol mol-1 yr-2. This slowing atmospheric growth is consistent 38 with HCFC-22 moving from dispersive (high fractional emissions) to feedstock (low fractional 39 emissions) uses, with HFC-23 emissions remaining as a consequence of incomplete mitigation 40 from all HCFC-22 production. 41