Abstract
Abstract. High-frequency, in situ observations from the Advanced Global Atmospheric Gases Experiment (AGAGE), for the period 2003 to 2012, combined with archive flask measurements dating back to 1977, have been used to capture the rapid growth of HFC-143a (CH3CF3) and HFC-32 (CH2F2) mole fractions and emissions into the atmosphere. Here we report the first in situ global measurements of these two gases. HFC-143a and HFC-32 are the third and sixth most abundant hydrofluorocarbons (HFCs) respectively and they currently make an appreciable contribution to the HFCs in terms of atmospheric radiative forcing (1.7 ± 0.04 and 0.7 ± 0.02 mW m−2 in 2012 respectively). In 2012 the global average mole fraction of HFC-143a was 13.4 ± 0.3 ppt (1σ) in the lower troposphere and its growth rate was 1.4 ± 0.04 ppt yr−1; HFC-32 had a global mean mole fraction of 6.2 ± 0.2 ppt and a growth rate of 1.1 ± 0.04 ppt yr−1 in 2012. The extensive observations presented in this work have been combined with an atmospheric transport model to simulate global atmospheric abundances and derive global emission estimates. It is estimated that 23 ± 3 Gg yr−1 of HFC-143a and 21 ± 11 Gg yr−1 of HFC-32 were emitted globally in 2012, and the emission rates are estimated to be increasing by 7 ± 5% yr−1 for HFC-143a and 14 ± 11% yr−1 for HFC-32.
Highlights
Hydrofluorocarbons (HFCs) were developed as replacements for ozone-depleting chlorofluorocarbons (CFCs) and hydrochlorofluorocarbons (HCFCs), which have mainly been used as working fluids in refrigerators and air conditioners, as blowing agents and active insulating component in plastic foams, as aerosol propellants and as fire retardants
In this paper we report HFC-32 and HFC-143a measurements of archived air samples collected at Cape Grim, Tasmania, and Northern Hemisphere (NH) archived air samples mostly collected at Trinidad Head, California, along with modern ambient measurements from the Advanced Global Atmospheric Gases Experiment (AGAGE; Prinn et al, 2000)
The observations show that the growth rate has been increasing throughout this time period
Summary
Hydrofluorocarbons (HFCs) were developed as replacements for ozone-depleting chlorofluorocarbons (CFCs) and hydrochlorofluorocarbons (HCFCs), which have mainly been used as working fluids in refrigerators and air conditioners, as blowing agents and active insulating component in plastic foams, as aerosol propellants and as fire retardants. HFCs are partially fluorinated hydrocarbons that have atmospheric lifetimes in the range of 1–50 years (with the exception of HFC-23 and HFC-236fa, which have lifetimes of 222 and 242 years respectively) and are removed from the atmosphere through reaction with tropospheric hydroxyl radicals (Ko et al, 2013; Forster et al, 2007) They are chlorinefree, and as such have effectively zero stratospheric ozone depletion potential and are not yet included in the Montreal Protocol and its subsequent amendments. National HFC data are submitted to the United Nations Framework Convention on Climate Change (UNFCCC) under the Rio Convention and Kyoto Protocol, and countries that have ratified the Kyoto Protocol (Annex I parties or developed countries and economies in transition) have committed over a short timescale (2008–2012) to reduce their emissions of greenhouse gases. It has been suggested that the total GWPweighted HFC emissions for baseline scenarios in 2050 will be ∼4 times larger than those previously reported in the Intergovernmental Panel on Climate Change (IPCC) Special
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