Increase in global emissions of HFC-23 despite near-total expected reductions

Under the Kigali Amendment to the Montreal Protocol, new controls are being implemented to reduce emissions of HFC-23 (CHF\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$${}_{3}$$\end{document}3), a by-product during the manufacture of HCFC-22 (CHClF\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$${}_{2}$$\end{document}2). Starting in 2015, China and India, who dominate global HCFC-22 production (75% in 2017), set out ambitious programs to reduce HFC-23 emissions. Here, we estimate that these measures should have seen global emissions drop by 87% between 2014 and 2017. Instead, atmospheric observations show that emissions have increased and in 2018 were higher than at any point in history (15.9 \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\pm \ 0.9\ {\rm{{Gg}}\ {{{yr}}}^{-1}}$$\end{document}±0.9Ggyr−1). Given the magnitude of the discrepancy between expected and observation-inferred emissions, it is likely that the reported reductions have not fully materialized or there may be substantial unreported production of HCFC-22, resulting in unaccounted-for HFC-23 by-product emissions. The difference between reported and observation-inferred estimates suggests that an additional ~309 Tg \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$${{\rm{CO}}}_{2}$$\end{document}CO2-equivalent emissions were added to the atmosphere between 2015 and 2017.

International agreements have been implemented to reduce emissions of hydrofluorocarbons (HFCs) to reduce their radiative forcing. Even though reported HFC-23 emissions are at a historical low, observations indicate that emissions have actually increased over recent years to higher levels than previously.

Nitrogen trifluoride global emissions estimated from updated atmospheric measurements

Nitrogen trifluoride (NF(3)) has potential to make a growing contribution to the Earth's radiative budget; however, our understanding of its atmospheric burden and emission rates has been limited. Based on a revision of our previous calibration and using an expanded set of atmospheric measurements together with an atmospheric model and inverse method, we estimate that the global emissions of NF(3) in 2011 were 1.18 ± 0.21 Gg⋅y(-1), or ∼20 Tg CO(2)-eq⋅y(-1) (carbon dioxide equivalent emissions based on a 100-y global warming potential of 16,600 for NF(3)). The 2011 global mean tropospheric dry air mole fraction was 0.86 ± 0.04 parts per trillion, resulting from an average emissions growth rate of 0.09 Gg⋅y(-2) over the prior decade. In terms of CO(2) equivalents, current NF(3) emissions represent between 17% and 36% of the emissions of other long-lived fluorinated compounds from electronics manufacture. We also estimate that the emissions benefit of using NF(3) over hexafluoroethane (C(2)F(6)) in electronics manufacture is significant-emissions of between 53 and 220 Tg CO(2)-eq⋅y(-1) were avoided during 2011. Despite these savings, total NF(3) emissions, currently ∼10% of production, are still significantly larger than expected assuming global implementation of ideal industrial practices. As such, there is a continuing need for improvements in NF(3) emissions reduction strategies to keep pace with its increasing use and to slow its rising contribution to anthropogenic climate forcing.