scholarly journals History of atmospheric SF<sub>6</sub> from 1973 to 2008

2010 ◽  
Vol 10 (5) ◽  
pp. 13519-13555
Author(s):  
M. Rigby ◽  
J. Mühle ◽  
B. R. Miller ◽  
R. G. Prinn ◽  
P. B. Krummel ◽  
...  
Keyword(s):  
Growth Rate ◽  
Sulfur Hexafluoride ◽  
Transport Model ◽  
In Situ Monitoring ◽  
Electron Capture Detection ◽  
Monitoring Site ◽  
Emission Rates ◽  
Chemical Transport Model ◽  
History Of ◽  
Global Emissions

Abstract. We present atmospheric sulfur hexafluoride (SF6) mole fractions and emissions estimates from the 1970s to 2008. Measurements were made of archived air samples starting from 1973 in the Northern Hemisphere and from 1978 in the Southern Hemisphere, using the Advanced Global Atmospheric Gases Experiment (AGAGE) gas chromatographic–mass spectrometric (GC-MS) systems. These measurements were combined with modern high-frequency GC-MS and GC-electron capture detection (ECD) data from AGAGE monitoring sites, to produce a unique air history of this potent greenhouse gas. Atmospheric mole fractions were found to have increased by more than an order of magnitude between 1973 and 2008. The 2008 growth rate was found to be the highest recorded, at 0.29 ± 0.02 pmol mol−1 yr−1. A three-dimensional chemical transport model and a minimum variance Bayesian inverse method was used to estimate annual emission rates using the measurements. Consistent with the mole fraction growth rate maximum, global emissions during 2008 were also found to be highest in the 1973–2008 period, reaching 7.5 ± 0.4 Ggyr−1 and surpassing the previous maximum in 1995. The 2008 values follow an increase in emissions of 50 ± 25% since 2000. A second global inversion which also incorporated National Oceanic and Atmospheric Administration (NOAA) flask measurements and in situ monitoring site data was found to agree well with the emissions derived using AGAGE measurements alone. By estimating continent-scale emissions using all available AGAGE and NOAA surface measurements covering the period 2004–2008, we find that it is likely that much of the global emissions rise during this five-year period originated primarily from Asian countries that do not report emissions to the United Nations Framework Convention on Climate Change (UNFCCC). We also find it likely that SF6 emissions reported to the UNFCCC were underestimated between at least 2004 and 2007.

scholarly journals History of atmospheric SF<sub>6</sub> from 1973 to 2008

2010 ◽  
Vol 10 (21) ◽  
pp. 10305-10320 ◽  
Author(s):  
M. Rigby ◽  
J. Mühle ◽  
B. R. Miller ◽  
R. G. Prinn ◽  
P. B. Krummel ◽  
...  
Keyword(s):  
Growth Rate ◽  
Sulfur Hexafluoride ◽  
A Priori Estimates ◽  
Transport Model ◽  
In Situ Monitoring ◽  
Electron Capture Detection ◽  
Monitoring Site ◽  
Emission Rates ◽  
Chemical Transport Model ◽  
Global Emissions

Abstract. We present atmospheric sulfur hexafluoride (SF6) mole fractions and emissions estimates from the 1970s to 2008. Measurements were made of archived air samples starting from 1973 in the Northern Hemisphere and from 1978 in the Southern Hemisphere, using the Advanced Global Atmospheric Gases Experiment (AGAGE) gas chromatographic-mass spectrometric (GC-MS) systems. These measurements were combined with modern high-frequency GC-MS and GC-electron capture detection (ECD) data from AGAGE monitoring sites, to produce a unique 35-year atmospheric record of this potent greenhouse gas. Atmospheric mole fractions were found to have increased by more than an order of magnitude between 1973 and 2008. The 2008 growth rate was the highest recorded, at 0.29 ± 0.02 pmolmol−1 yr−1. A three-dimensional chemical transport model and a minimum variance Bayesian inverse method was used to estimate annual emission rates using the measurements, with a priori estimates from the Emissions Database for Global Atmospheric Research (EDGAR, version 4). Consistent with the mole fraction growth rate maximum, global emissions during 2008 were also the highest in the 1973–2008 period, reaching 7.4 ± 0.6 Gg yr−1 (1-σ uncertainties) and surpassing the previous maximum in 1995. The 2008 values follow an increase in emissions of 48 ± 20% since 2001. A second global inversion which also incorporated National Oceanic and Atmospheric Administration (NOAA) flask measurements and in situ monitoring site data agreed well with the emissions derived using AGAGE measurements alone. By estimating continent-scale emissions using all available AGAGE and NOAA surface measurements covering the period 2004–2008, with no pollution filtering, we find that it is likely that much of the global emissions rise during this five-year period originated primarily from Asian developing countries that do not report detailed, annual emissions to the United Nations Framework Convention on Climate Change (UNFCCC). We also find it likely that SF6 emissions reported to the UNFCCC were underestimated between at least 2004 and 2005.

scholarly journals Improving measurements of SF<sub>6</sub> for the study of atmospheric transport and emissions

2011 ◽  
Vol 4 (11) ◽  
pp. 2441-2451 ◽  
Author(s):  
B. D. Hall ◽  
G. S. Dutton ◽  
D. J. Mondeel ◽  
J. D. Nance ◽  
M. Rigby ◽  
...  
Keyword(s):  
Growth Rate ◽  
Sulfur Hexafluoride ◽  
Atmospheric Transport ◽  
Electron Capture Detection ◽  
Transport Models ◽  
Mixing Ratios ◽  
Economic Output ◽  
World Economic ◽  
Atmospheric Tracer ◽  
Global Emissions

Abstract. Sulfur hexafluoride (SF6) is a potent greenhouse gas and useful atmospheric tracer. Measurements of SF6 on global and regional scales are necessary to estimate emissions and to verify or examine the performance of atmospheric transport models. Typical precision for common gas chromatographic methods with electron capture detection (GC-ECD) is 1–2%. We have modified a common GC-ECD method to achieve measurement precision of 0.5% or better. Global mean SF6 measurements were used to examine changes in the growth rate of SF6 and corresponding SF6 emissions. Global emissions and mixing ratios from 2000–2008 are consistent with recently published work. More recent observations show a 10% decline in SF6 emissions in 2008–2009, which seems to coincide with a decrease in world economic output. This decline was short-lived, as the global SF6 growth rate has recently increased to near its 2007–2008 maximum value of 0.30±0.03 pmol mol−1 (ppt) yr−1 (95% C.L.).

scholarly journals Improving measurements of SF<sub>6</sub> for the study of atmospheric transport and emissions

2011 ◽  
Vol 4 (4) ◽  
pp. 4131-4163 ◽  
Author(s):  
B. D. Hall ◽  
G. S. Dutton ◽  
D. J. Mondeel ◽  
J. D. Nance ◽  
M. Rigby ◽  
...  
Keyword(s):  
Growth Rate ◽  
Sulfur Hexafluoride ◽  
Atmospheric Transport ◽  
Measurement Precision ◽  
Electron Capture Detection ◽  
Mixing Ratios ◽  
Economic Output ◽  
World Economic ◽  
Atmospheric Tracer ◽  
Global Emissions

Abstract. Sulfur hexafluoride (SF6) is a potent greenhouse gas and useful atmospheric tracer. Measurements of SF6 on global and regional scales are necessary to estimate emissions and to verify or examine the performance of atmospheric transport models. Typical precision for common gas chromatographic methods with electron capture detection (GC-ECD) is 1–2 %. A method for improving measurement precision is described. We have modified a common GC-ECD method to achieve measurement precision of 0.5 % or better. Global mean SF6 measurements were used to examine changes in the growth rate of SF6 and corresponding SF6 emissions. Global emissions and mixing ratios from 2000–2008 are consistent with recently published work. More recent observations show a 10 % decline in SF6 emissions in 2008–2009, which seems to coincide with a decrease in world economic output. This decline was short-lived, as the global SF6 growth rate has recently increased to near its 2007–2008 maximum value of 0.30 ± 0.03 pmol mol−1 (ppt) yr−1 (95 % C.L.).

scholarly journals Attribution of recent increases in atmospheric methane through 3-D inverse modelling

2018 ◽  
Author(s):  
Joe McNorton ◽  
Chris Wilson ◽  
Manuel Gloor ◽  
Rob Parker ◽  
Hartmut Boesch ◽  
...  
Keyword(s):  
Growth Rate ◽  
Transport Model ◽  
Energy Sector ◽  
Total Carbon ◽  
Sensitivity Analyses ◽  
Northern Eurasia ◽  
Atmospheric Methane ◽  
Chemical Transport Model ◽  
Bottom Up ◽  
Source And Sink

Abstract. The atmospheric methane (CH4) growth rate has varied considerably in recent decades. Unexplained renewed growth after 2006 followed seven years of stagnation and coincided with an isotopic trend toward CH4 more depleted in 13C, suggesting changes in sources and/or sinks. Using surface observations of both CH4 and the isotopologue ratio value (δ13CH4) to constrain a global 3D chemical transport model (CTM), we have performed a synthesis inversion for source and sink attribution. Our method extends on previous studies by providing monthly and regional attribution of emissions from 6 different sectors and changes in atmospheric sinks for the extended 2003–2015 period. Regional evaluation of the model CH4 tracer with independent column observations from the Greenhouse gases Observing SATellite (GOSAT) shows improved performance when using posterior fluxes (R = 0.94–0.96, RMSE = 8.3–16.5 ppb), relative to prior fluxes (R = 0.60–0.92, RMSE = 48.6–64.6 ppb). Further independent validation with data from the Total Carbon Column Observing Network (TCCON) shows a similar improvement in the posterior fluxes (R = 0.90, RMSE = 21.4 ppb) compared to the prior (R = 0.71, RMSE = 55.3 ppb). Based on these improved posterior fluxes, the inversion results suggest the most likely cause of the renewed methane growth is a post-2006 1.8 ± 0.4 % decrease in mean OH, a 12.9 ± 2.7 % increase in energy sector emissions, mainly from Africa/Middle East and Southern Asia/Oceania, and a 2.6 ± 1.8 % increase in wetland emissions, mainly from Northern Eurasia. The posterior wetland increases are in general agreement with bottom-up estimates, but the energy sector growth is greater than estimated by bottom-up methods. The model results are consistent across a range of sensitivity analyses performed. When forced to assume a constant (annually repeating) OH distribution, the inversion requires a greater increase in energy sector (13.6 ± 2.7 %) and wetland (3.6 ± 1.8 %) emissions but also introduces an 11.5 ± 3.8 % decrease in biomass burning emissions. Assuming no prior trend in sources and sinks slightly reduces the posterior growth rate in energy sector and wetland emissions and further increases the amplitude of the negative OH trend. We find that possible tropospheric Cl variations do not to influence δ13CH4 and CH4 trends, although we suggest further work on Cl variability is required to fully diagnose this contribution. While the study provides quantitative insight into possible emissions variations which may explain the observed trends, uncertainty in prior source and sink estimates and a paucity of δ13CH4 observations limit the accuracy of the posterior estimates.

scholarly journals Global emissions of HFC-143a (CH<sub>3</sub>CF<sub>3</sub>) and HFC-32 (CH<sub>2</sub>F<sub>2</sub>) from in situ and air archive atmospheric observations

2014 ◽  
Vol 14 (17) ◽  
pp. 9249-9258 ◽  
Author(s):  
S. O'Doherty ◽  
M. Rigby ◽  
J. Mühle ◽  
D. J. Ivy ◽  
B. R. Miller ◽  
...  
Keyword(s):  
Growth Rate ◽  
Mole Fraction ◽  
Radiative Forcing ◽  
Transport Model ◽  
Atmospheric Transport ◽  
Lower Troposphere ◽  
Emission Rates ◽  
Global Emission ◽  
Atmospheric Observations

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.

scholarly journals Global emissions of HFC-143a (CH<sub>3</sub>CF<sub>3</sub>) and HFC-32 (CH<sub>2</sub>F<sub>2</sub>) from in situ and air archive atmospheric observations

2014 ◽  
Vol 14 (5) ◽  
pp. 6471-6500 ◽  
Author(s):  
S. O'Doherty ◽  
M. Rigby ◽  
J. Mühle ◽  
D. J. Ivy ◽  
B. R. Miller ◽  
...  
Keyword(s):  
Growth Rate ◽  
Mole Fraction ◽  
Radiative Forcing ◽  
Transport Model ◽  
Atmospheric Transport ◽  
Lower Troposphere ◽  
Emission Rates ◽  
Global Emission ◽  
Atmospheric Observations

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 HFCs respectively and they currently make an appreciable contribution to the HFCs in terms of atmospheric radiative forcing (1.7 and 0.7 mW m2 in 2012, respectively). In 2012 the global average mole fraction of HFC-143a was 13.4 ± 0.3 ppt (1-sigma) 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 7 ± 5% yr−1 for HFC-143a and 14 ± 11% yr−1 for HFC-32.

scholarly journals Global emission estimates and radiative impact of C<sub>4</sub>F<sub>10</sub>, C<sub>5</sub>F<sub>12</sub>, C<sub>6</sub>F<sub>14</sub>, C<sub>7</sub>F<sub>16</sub> and C<sub>8</sub>F<sub>18</sub>

2012 ◽  
Vol 12 (5) ◽  
pp. 12987-13014 ◽  
Author(s):  
D. J. Ivy ◽  
M. Rigby ◽  
M. Baasandorj ◽  
J. B. Burkholder ◽  
R. G. Prinn
Keyword(s):  
Molecular Weight ◽  
High Molecular Weight ◽  
Transport Model ◽  
Emission Rates ◽  
Chemical Transport Model ◽  
Bottom Up ◽  
Radiative Efficiency ◽  
Atmospheric Species ◽  
Global Emission ◽  
Atmospheric Observations

Abstract. Global emission estimates based on new atmospheric observations are presented for the acylic high molecular weight perfluorocarbons (PFCs): decafluorobutane (C4F10), dodecafluoropentane (C5F12), tetradecafluorohexane (C6F14), hexadecafluoroheptane (C7F16) and octadecafluorooctane (C8F18). Emissions are estimated using a 3-dimensional chemical transport model and an inverse method that includes a growth constraint on emissions. The observations used in the inversion are based on newly measured archived air samples that cover a 39-yr period, from 1973 to 2011, and include 36 Northern Hemispheric and 46 Southern Hemispheric samples (Ivy et al., 2012). The derived emission estimates show that global emission rates were largest in the 1980s and 1990s for C4F10 and C5F12, and in the 1990s for C6F14,C7F16 and C8F18. After a subsequent decline, emissions have remained relatively stable, within 20%, for the last 5 yr. Bottom-up emission estimates are available from the Emission Database for Global Atmospheric Research version 4.2 (EDGARv4.2) for C4F10, C5F12, C6F14 and C7F16, and inventories of C4F10, C5F12 andC6F14 are reported to the United Nations' Framework Convention on Climate Change (UNFCCC) by Annex 1 countries that have ratified the Kyoto Protocol. The atmospheric measurement based emission estimates are 20 times larger than EDGARv4.2 for C4F10 and over three orders of magnitude for C5F12. The derived emission estimates for C6F14 largely agree with the bottom-up estimates from EDGARv4.2. Moreover, the C7F16 emission estimates are comparable to those of EDGARv4.2 at their peak in the 1990s, albeit significant underestimation for the other time periods. There are no bottom-up emission estimates for C8F18, thus the emission rates reported here are the first for C8F18. The reported inventories for C4F10, C5F12 and C6F14 to UNFCCC are five to ten times lower than those estimated in this study. In addition, we present measured infrared absorption spectra for C7F16 and C8F18, and estimate their radiative efficiencies and global warming potentials (GWPs). We find that C8F18's radiative efficiency is similar to trifluoromethyl sulfur pentafluoride's (SF5CF3) at 0.57 W m−2 ppb−1, which is the highest radiative efficiency of any measured atmospheric species. Using the 100-yr time horizon GWPs, the high molecular weight perfluorocarbons studied here contributed up to 15.4% of the total PFC emissions in CO2 equivalents in 1997 and 6% of the total PFC emissions in 2009.

scholarly journals Current estimates of biogenic emissions from Eucalypts uncertain for Southeast Australia

2016 ◽  
Author(s):  
K. M. Emmerson ◽  
I. E. Galbally ◽  
A. B. Guenther ◽  
C. Paton-Walsh ◽  
E.-A. Guerette ◽  
...  
Keyword(s):  
Transport Model ◽  
Chemical Species ◽  
Field Measurements ◽  
Oxidation Products ◽  
Biogenic Emissions ◽  
Emission Rates ◽  
Chemical Transport Model ◽  
Southeast Australia ◽  
Unusual Position ◽  
Adult Trees

Abstract. The biogenic emissions of isoprene and monoterpenes are one of the main drivers of atmospheric photochemistry, including oxidant and secondary organic aerosol production. In this paper, the emission rates of isoprene and monoterpenes from Australian vegetation are investigated for the first time using the Model of Emissions of Gases and Aerosols from Nature version 2.1 (MEGANv2.1), the CSIRO chemical transport model, and atmospheric observations of isoprene, monoterpenes and isoprene oxidation products (methacrolein and methyl-vinyl-ketone). Observations from four field campaigns during three different seasons are used, covering urban, coastal suburban and inland forest areas. The observed concentrations of isoprene and monoterpenes were of a broadly similar magnitude, which may indicate that southeast Australia holds an unusual position where neither chemical species dominates. The model results overestimate the observed atmospheric concentrations of isoprene (up to a factor of 6) and underestimate the monoterpene concentrations (up to a factor of 4). This may occur because the emission rates currently used in MEGANv2.1 for Australia are drawn mainly from young Eucalypt trees (< 7 years), which may emit more isoprene than adult trees. There is no single increase/decrease factor for the emissions which suits all seasons and conditions studied. There is a need for further field measurements of in-situ isoprene and monoterpene emission fluxes in Australia.

scholarly journals Global emission estimates and radiative impact of C4F10, C5F12, C6F14, C7F16 and C8F18

2012 ◽  
Vol 12 (16) ◽  
pp. 7635-7645 ◽  
Author(s):  
D. J. Ivy ◽  
M. Rigby ◽  
M. Baasandorj ◽  
J. B. Burkholder ◽  
R. G. Prinn
Keyword(s):  
Molecular Weight ◽  
High Molecular Weight ◽  
Transport Model ◽  
Emission Rates ◽  
Chemical Transport Model ◽  
Cumulative Emission ◽  
Bottom Up ◽  
Radiative Efficiency ◽  
Global Emission ◽  
Radiative Impact

Abstract. Global emission estimates based on new atmospheric observations are presented for the acylic high molecular weight perfluorocarbons (PFCs): decafluorobutane (C4F10), dodecafluoropentane (C5F12), tetradecafluorohexane (C6F14), hexadecafluoroheptane (C7F16) and octadecafluorooctane (C8F18). Emissions are estimated using a 3-dimensional chemical transport model and an inverse method that includes a growth constraint on emissions. The observations used in the inversion are based on newly measured archived air samples that cover a 39-yr period, from 1973 to 2011, and include 36 Northern Hemispheric and 46 Southern Hemispheric samples. The derived emission estimates show that global emission rates were largest in the 1980s and 1990s for C4F10 and C5F12, and in the 1990s for C6F14, C7F16 and C8F18. After a subsequent decline, emissions have remained relatively stable, within 20%, for the last 5 yr. Bottom-up emission estimates are available from the Emission Database for Global Atmospheric Research version 4.2 (EDGARv4.2) for C4F10, C5F12, C6F14 and C7F16, and inventories of C4F10, C5F12 and C6F14 are reported to the United Nations' Framework Convention on Climate Change (UNFCCC) by Annex 1 countries that have ratified the Kyoto Protocol. The atmospheric measurement-based emission estimates are 20 times larger than EDGARv4.2 for C4F10 and over three orders of magnitude larger for C5F12 (with 2008 EDGARv4.2 estimates for C5F12 at 9.6 kg yr−1, as compared to 67±53 t yr−1 as derived in this study). The derived emission estimates for C6F14 largely agree with the bottom-up estimates from EDGARv4.2. Moreover, the C7F16 emission estimates are comparable to those of EDGARv4.2 at their peak in the 1990s, albeit significant underestimation for the other time periods. There are no bottom-up emission estimates for C8F18, thus the emission rates reported here are the first for C8F18. The reported inventories for C4F10, C5F12 and C6F14 to UNFCCC are five to ten times lower than those estimated in this study. In addition, we present measured infrared absorption spectra for C7F16 and C8F18, and estimate their radiative efficiencies and global warming potentials (GWPs). We find that C8F18's radiative efficiency is similar to trifluoromethyl sulfur pentafluoride's (SF5F3) at 0.57 W m−2 ppb−1, which is the highest radiative efficiency of any measured atmospheric species. Using the 100-yr time horizon GWPs, the total radiative impact of the high molecular weight perfluorocarbons emissions are also estimated; we find the high molecular weight PFCs peak contribution was in 1997 at 24 000 Gg of carbon dioxide (CO2) equivalents and has decreased by a factor of three to 7300 Gg of CO2 equivalents in 2010. This 2010 cumulative emission rate for the high molecular weight PFCs is comparable to: 0.02% of the total CO2 emissions, 0.81% of the total hydrofluorocarbon emissions, or 1.07% of the total chlorofluorocarbon emissions projected for 2010 (Velders et al., 2009). In terms of the total PFC emission budget, including the lower molecular weight PFCs, the high molecular weight PFCs peak contribution was also in 1997 at 15.4% and was 6% of the total PFC emissions in CO2 equivalents in 2009.

scholarly journals Recent increases in the atmospheric growth rate and emissions of HFC-23 (CHF<sub>3</sub>) and the link to HCFC-22 (CHClF<sub>2</sub>) production

2017 ◽  
Author(s):  
Peter G. Simmonds ◽  
Matthew Rigby ◽  
Archie McCulloch ◽  
Martin K. Vollmer ◽  
Stephan Henne ◽  
...  
Keyword(s):  
Growth Rate ◽  
Mole Fraction ◽  
Radiative Forcing ◽  
Average Rate ◽  
Time Frame ◽  
Atmospheric Gases ◽  
Annual Average ◽  
History Of ◽  
Global Emissions ◽  
Cape Grim

Abstract. High frequency measurements of the potent hydrofluorocarbon greenhouse gas CHF3 (HFC-23), a by-product of production of the hydrochlorofluorocarbon HCFC-22 (CHClF2), at five core stations of the Advanced Global Atmospheric Gases Experiment (AGAGE) network, combined with measurements of firn and Cape Grim Air Archive (CGAA) air samples, are used to explore the changing atmospheric abundance of HFC-23. These measurements are used in combination with the AGAGE 2-D atmospheric 12-box model and a Bayesian inversion methodology to determine model atmospheric mole fractions and the atmospheric history of global HFC-23 emissions. The global modelled annual mole fraction of HFC-23 in the background atmosphere was 28.9 ± 0.6 pmol mol−1 at the end of 2016, representing a 28 % increase from 22.6 ± 0.4 pmol mol−1 in 2009. Over the same time frame, the modelled mole fraction of HCFC-22 increased by 19 % from 199 ± 2 pmol mol−1 to 237 ± 2 pmol mol−1. However, the annual average HCFC-22 growth rate decelerated from 2009 to 2016 at an annual average rate of 0.5 pmol mol−1 yr−2. Our results demonstrate that, following a minimum in HFC-23 global emissions in 2009 of 9.6 ± 0.6 Gg yr−1, emissions increased to a maximum in 2014 of 14.5 ± 0.6 Gg yr−1, declining to 12.7 ± 0.6 Gg yr−1 (157 Mt  CO2-eq. yr−1) in 2016. The 2009 emissions minimum is consistent with estimates based on national reports and is likely a response to the implementation of the Clean Development Mechanism (CDM) to mitigate HFC-23 emissions by incineration in developing (Non-Annex 1) countries under the Kyoto Protocol. Our derived cumulative emissions of HFC-23 during 2010–2016 were 89 ± 2 Gg (1.1 ± 0.2 Gt CO2-eq), which led to an increase in radiative forcing of 1.0 ± 0.1 mW m−2. Although the CDM had reduced global HFC-23 emissions, it cannot now offset the radiative forcing of higher emissions from increasing HCFC-22 production in Non-Annex 1 countries, as the CDM was closed to new entrants in 2009. We also find that the cumulative European HFC-23 emissions from 2010 to 2016 were ~ 1.3 Gg, corresponding to just 1.5 % of cumulative global HFC-23 emissions over this same period.

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