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Saikawa, E, Rigby M, Prinn RG, Montzka SA, Miller BR, Kuijpers LJM, Fraser PJB, Vollmer MK, Saito T, Yokouchi Y, Harth CM, Muhle J, Weiss RF, Salameh PK, Kim J, Li S, Park S, Kim KR, Young D, O'Doherty S, Simmonds PG, McCulloch A, Krummel PB, Steele LP, Lunder C, Hermansen O, Maione M, Arduini J, Yao B, Zhou LX, Wang HJ, Elkins JW, Hall B.  2012.  Global and regional emission estimates for HCFC-22. Atmospheric Chemistry and Physics. 12:10033-10050.   10.5194/acp-12-10033-2012   AbstractWebsite

HCFC-22 (CHClF2, chlorodifluoromethane) is an ozone-depleting substance (ODS) as well as a significant greenhouse gas (GHG). HCFC-22 has been used widely as a refrigerant fluid in cooling and air-conditioning equipment since the 1960s, and it has also served as a traditional substitute for some chlorofluorocarbons (CFCs) controlled under the Montreal Protocol. A low frequency record on tropospheric HCFC-22 since the late 1970s is available from measurements of the Southern Hemisphere Cape Grim Air Archive (CGAA) and a few Northern Hemisphere air samples (mostly from Trinidad Head) using the Advanced Global Atmospheric Gases Experiment (AGAGE) instrumentation and calibrations. Since the 1990s high-frequency, high-precision, in situ HCFC-22 measurements have been collected at these AGAGE stations. Since 1992, the Global Monitoring Division of the National Oceanic and Atmospheric Administration/Earth System Research Laboratory (NOAA/ESRL) has also collected flasks on a weekly basis from remote sites across the globe and analyzed them for a suite of halocarbons including HCFC-22. Additionally, since 2006 flasks have been collected approximately daily at a number of tower sites across the US and analyzed for halocarbons and other gases at NOAA. All results show an increase in the atmospheric mole fractions of HCFC-22, and recent data show a growth rate of approximately 4% per year, resulting in an increase in the background atmospheric mole fraction by a factor of 1.7 from 1995 to 2009. Using data on HCFC-22 consumption submitted to the United Nations Environment Programme (UNEP), as well as existing bottom-up emission estimates, we first create globally-gridded a priori HCFC-22 emissions over the 15 yr since 1995. We then use the three-dimensional chemical transport model, Model for Ozone and Related Chemical Tracers version 4 (MOZART v4), and a Bayesian inverse method to estimate global as well as regional annual emissions. Our inversion indicates that the global HCFC-22 emissions have an increasing trend between 1995 and 2009. We further find a surge in HCFC-22 emissions between 2005 and 2009 from developing countries in Asia - the largest emitting region including China and India. Globally, substantial emissions continue despite production and consumption being phased out in developed countries currently.

Prinn, RG, Weiss RF, Arduini J, Arnold T, DeWitt HL, Fraser PJ, Ganesan AL, Gasore J, Harth CM, Hermansen O, Kim J, Krummel PB, Li SL, Loh ZM, Lunder CR, Maione M, Manning AJ, Miller B, Mitrevski B, Muhle J, O'Doherty S, Park S, Reimann S, Rigby M, Saito T, Salameh PK, Schmidt R, Simmonds PG, Steele LP, Vollmer MK, Wang RH, Yao B, Yokouchi Y, Young D, Zhou LX.  2018.  History of chemically and radiatively important atmospheric gases from the Advanced Global Atmospheric Gases Experiment (AGAGE). Earth System Science Data. 10:985-1018.   10.5194/essd-10-985-2018   AbstractWebsite

We present the organization, instrumentation, datasets, data interpretation, modeling, and accomplishments of the multinational global atmospheric measurement program AGAGE (Advanced Global Atmospheric Gases Experiment). AGAGE is distinguished by its capability to measure globally, at high frequency, and at multiple sites all the important species in the Montreal Protocol and all the important non-carbon-dioxide (non-CO2) gases assessed by the Intergovernmental Panel on Climate Change (CO2 is also measured at several sites). The scientific objectives of AGAGE are important in furthering our understanding of global chemical and climatic phenomena. They are the following: (1) to accurately measure the temporal and spatial distributions of anthropogenic gases that contribute the majority of reactive halogen to the stratosphere and/or are strong infrared absorbers (chlorocarbons, chlorofluorocarbons CFCs, bromocarbons, hydrochlorofluorocarbons HCFCs, hydrofluorocarbons HFCs and polyfluorinated compounds (perfluorocarbons PFCs), nitrogen trifluoride NF3, sulfuryl fluoride SO2F2, and sulfur hexafluoride SF6) and use these measurements to determine the global rates of their emission and/or destruction (i.e., lifetimes); (2) to accurately measure the global distributions and temporal behaviors and determine the sources and sinks of non-CO2 biogenic anthropogenic gases important to climate change and/or ozone depletion (methane CH4, nitrous oxide N20, carbon monoxide CO, molecular hydrogen H2, methyl chloride CH3C1, and methyl bromide CH3Br); (3) to identify new long-lived greenhouse and ozone -depleting gases (e.g., SO2F2, NF3, heavy PFCs (C4Fm, C5F12, C6F 14, C7F16, and C8F18) and hydrofluoroolefins (HF0s; e.g., CH2 = CFCF3) have been identified in AGAGE), initiate the real-time monitoring of these new gases, and reconstruct their past histories from AGAGE, air archive, and firn air measurements; (4) to determine the average concentrations and trends of tropospheric hydroxyl radicals (OH) from the rates of destruction of atmospheric trichloroethane (CH3CC13), HFCs, and HCFCs and estimates of their emissions; (5) to determine from atmospheric observations and estimates of their destruction rates the magnitudes and distributions by region of surface sources and sinks of all measured gases; (6) to provide accurate data on the global accumulation of many of these trace gases that are used to test the synoptic-, regional-, and global -scale circulations predicted by three-dimensional models; and (7) to provide global and regional measurements of methane, carbon monoxide, and molecular hydrogen and estimates of hydroxyl levels to test primary atmospheric oxidation pathways at midlatitudes and the tropics. Network Information and Data Repository: http://agage.mit.edu/data or http://cdiac.ess-dive.lbl.gov/ndps/alegage.html (https://doi.org/10.3334/CDIAC/atg.db1001).

Simmonds, PG, Rigby M, McCulloch A, Vollmer MK, Henne S, Muhle J, O'Doherty S, Manning AJ, Krummel PB, Fraser PJ, Young D, Weiss RF, Salameh PK, Harth CM, Reimann S, Trudinger CM, Steele LP, Wang RHJ, Ivy DJ, Prinn RG, Mitrevski B, Etheridge DM.  2018.  Recent increases in the atmospheric growth rate and emissions of HFC-23 (CHF3) and the link to HCFC-22 (CHClF2) production. Atmospheric Chemistry and Physics. 18:4153-4169.   10.5194/acp-18-4153-2018   AbstractWebsite

High frequency measurements of trifluoromethane (HFC-23, CHF3), a potent hydrofluorocarbon greenhouse gas, largely emitted to the atmosphere as a by-product of the production of the hydrochlorofluorocarbon HCFC-22 (CHClF2), at five core stations of the Advanced Global Atmospheric Gases Experiment (AGAGE) network, combined with measurements on firn air, old Northern Hemisphere air samples and Cape Grim Air Archive (CGAA) air samples, are used to explore the current and historic changes in the 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 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 to 237 +/- 2 pmol mol(-1). However, unlike HFC-23, the annual average HCFC-22 growth rate slowed from 2009 to 2016 at an annual average rate of -0.5 pmol mol(-1) yr(-2). This slowing atmospheric growth is consistent with HCFC-22 moving from dispersive (high fractional emissions) to feedstock (low fractional emissions) uses, with HFC-23 emissions remaining as a consequence of incomplete mitigation from all HCFC-22 production. Our results demonstrate that, following a minimum in HFC-23 global emissions in 2009 of 9.6 +/- 0.6, emissions increased to a maximum in 2014 of 14.5 +/- 0.6 Gg yr(-1) and then declined to 12.7 +/- 0.6 Gg yr(-1) (157 MtCO(2) 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 20102016 were 89 +/- 2 Gg (1.1 +/- 0.2 GtCO(2) eq.), which led to an increase in radiative forcing of 1.0 +/- 0.1mWm(-2) over the same period. Although the CDM had reduced global HFC-23 emissions, it cannot now offset the 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 similar to 1.3 Gg, corresponding to just 1.5% of cumulative global HFC-23 emissions over this same period. The majority of the increase in global HFC-23 emissions since 2010 is attributed to a delay in the adoption of mitigation technologies, predominantly in China and East Asia. However, a reduction in emissions is anticipated, when the Kigali 2016 amendment to the Montreal Protocol, requiring HCFC and HFC production facilities to introduce destruction of HFC-23, is fully implemented.

Lunt, MF, Rigby M, Ganesan AL, Manning AJ, Prinn RG, O'Doherty S, Muhle J, Harth CM, Salameh PK, Arnold T, Weiss RF, Saito T, Yokouchi Y, Krummel PB, Steele LP, Fraser PJ, Li SL, Park S, Reimann S, Vollmer MK, Lunder C, Hermansen O, Schmidbauer N, Maione M, Arduini J, Young D, Simmonds PG.  2015.  Reconciling reported and unreported HFC emissions with atmospheric observations. Proceedings of the National Academy of Sciences of the United States of America. 112:5927-5931.   10.1073/pnas.1420247112   AbstractWebsite

We infer global and regional emissions of five of the most abundant hydrofluorocarbons (HFCs) using atmospheric measurements from the Advanced Global Atmospheric Gases Experiment and the National Institute for Environmental Studies, Japan, networks. We find that the total CO2-equivalent emissions of the five HFCs from countries that are required to provide detailed, annual reports to the United Nations Framework Convention on Climate Change (UNFCCC) increased from 198 (175-221) Tg-CO2-eq.y(-1) in 2007 to 275 (246-304) Tg-CO2-eq.y(-1) in 2012. These global warming potential-weighted aggregated emissions agree well with those reported to the UNFCCC throughout this period and indicate that the gap between reported emissions and global HFC emissions derived from atmospheric trends is almost entirely due to emissions from nonreporting countries. However, our measurement-based estimates of individual HFC species suggest that emissions, from reporting countries, of the most abundant HFC, HFC-134a, were only 79% (63-95%) of the UNFCCC inventory total, while other HFC emissions were significantly greater than the reported values. These results suggest that there are inaccuracies in the reporting methods for individual HFCs, which appear to cancel when aggregated together.