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2019
Fang, XK, Park S, Saito T, Tunnicliffe R, Ganesan AL, Rigby M, Li SL, Yokouchi Y, Fraser PJ, Harth CM, Krummel PB, Muhle J, O'Doherty S, Salameh PK, Simmonds PG, Weiss RF, Young D, Lunt MF, Manning AJ, Gressentl A, Prinn RG.  2019.  Rapid increase in ozone-depleting chloroform emissions from China. Nature Geoscience. 12:89-+.   10.1038/s41561-018-0278-2   AbstractWebsite

Chloroform contributes to the depletion of the stratospheric ozone layer. However, due to its short lifetime and predominantly natural sources, it is not included in the Montreal Protocol that regulates the production and uses of ozone-depleting substances. Atmospheric chloroform mole fractions were relatively stable or slowly decreased during 1990-2010. Here we show that global chloroform mole fractions increased after 2010, based on in situ chloroform measurements at seven stations around the world. We estimate that the global chloroform emissions grew at the rate of 3.5% yr(-1) between 2010 and 2015 based on atmospheric model simulations. We used two regional inverse modelling approaches, combined with observations from East Asia, to show that emissions from eastern China grew by 49 (41-59) Gg between 2010 and 2015, a change that could explain the entire increase in global emissions. We suggest that if chloroform emissions continuously grow at the current rate, the recovery of the stratospheric ozone layer above Antarctica could be delayed by several years.

2018
Arnold, T, Manning AJ, Kim J, Li SL, Webster H, Thomson D, Muhle J, Weiss RF, Park S, O'Doherty S.  2018.  Inverse modelling of CF4 and NF3 emissions in East Asia. Atmospheric Chemistry and Physics. 18:13305-13320.   10.5194/acp-18-13305-2018   AbstractWebsite

Decadal trends in the atmospheric abundances of carbon tetrafluoride (CF4) and nitrogen trifluoride (NF3) have been well characterised and have provided a time series of global total emissions. Information on locations of emissions contributing to the global total, however, is currently poor. We use a unique set of measurements between 2008 and 2015 from the Gosan station, Jeju Island, South Korea (part of the Advanced Global Atmospheric Gases Experiment network), together with an atmospheric transport model, to make spatially disaggregated emission estimates of these gases in East Asia. Due to the poor availability of good prior information for this study, our emission estimates are largely influenced by the atmospheric measurements. Notably, we are able to highlight emission hotspots of NF3 and CF4 in South Korea due to the measurement location. We calculate emissions of CF4 to be quite constant between the years 2008 and 2015 for both China and South Korea, with 2015 emissions calculated at 4.3 +/- 2.7 and 0.36 +/- 0.11 Gg yr(-1), respectively. Emission estimates of NF3 from South Korea could be made with relatively small uncertainty at 0.6 +/- 0.07 Gg yr(-1) in 2015, which equates to similar to 1.6% of the country's CO2 emissions. We also apply our method to calculate emissions of CHF3 (HFC-23) between 2008 and 2012, for which our results find good agreement with other studies and which helps support our choice in methodology for CF4 and NF3.

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).

Elvidge, EL, Bonisch H, Brenninkmeijer CAM, Engel A, Fraser PJ, Gallacher E, Langenfelds R, Muhle J, Oram DE, Ray EA, Ridley AR, Rockmann T, Sturges WT, Weiss RF, Laube JC.  2018.  Evaluation of stratospheric age of air from CF4, C2F6, C3F8, CHF3, HFC-125, HFC-227ea and SF6; implications for the calculations of halocarbon lifetimes, fractional release factors and ozone depletion potentials. Atmospheric Chemistry and Physics. 18:3369-3385.   10.5194/acp-18-3369-2018   AbstractWebsite

In a changing climate, potential stratospheric circulation changes require long-term monitoring. Stratospheric trace gas measurements are often used as a proxy for stratospheric circulation changes via the "mean age of air" values derived from them. In this study, we investigated five potential age of air tracers - the perfluorocarbons CF4, C2F6 and C3F8 and the hydrofluorocarbons CHF3 (HFC-23) and HFC-125 - and compare them to the traditional tracer SF6 and a (relatively) shorter-lived species, HFC-227ea. A detailed uncertainty analysis was performed on mean ages derived from these "new" tracers to allow us to confidently compare their efficacy as age tracers to the existing tracer, SF6. Our results showed that uncertainties associated with the mean age derived from these new age tracers are similar to those derived from SF6, suggesting that these alternative compounds are suitable in this respect for use as age tracers. Independent verification of the suitability of these age tracers is provided by a comparison between samples analysed at the University of East Anglia and the Scripps Institution of Oceanography. All five tracers give younger mean ages than SF6, a discrepancy that increases with increasing mean age. Our findings qualitatively support recent work that suggests that the stratospheric lifetime of SF6 is significantly less than the previous estimate of 3200 years. The impact of these younger mean ages on three policy-relevant parameters - stratospheric lifetimes, fractional release factors (FRFs) and ozone depletion potentials - is investigated in combination with a recently improved methodology to calculate FRFs. Updates to previous estimations for these parameters are provided.

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.

Vollmer, MK, Young D, Trudinger CM, Muhle J, Henne S, Rigby M, Park S, Li S, Guillevic M, Mitrevski B, Harth CM, Miller BR, Reimann S, Yao B, Steele LP, Wyss SA, Lunder CR, Arduini J, McCulloch A, Wu S, Rhee TS, Wang RHJ, Salameh PK, Hermansen O, Hill M, Langenfelds RL, Ivy D, O'Doherty S, Krummel PB, Maione M, Etheridge DM, Zhou LX, Fraser PJ, Prinn RG, Weiss RF, Simmonds PG.  2018.  Atmospheric histories and emissions of chlorofluorocarbons CFC-13 (CClF3), Sigma CFC-114 (C2Cl2F4), and CFC-115 (C2ClF5). Atmospheric Chemistry and Physics. 18:979-1002.   10.5194/acp-18-979-2018   AbstractWebsite

Based on observations of the chlorofluorocarbons CFC-13 (chlorotrifluoromethane), Sigma CFC-114 (combined measurement of both isomers of dichlorotetrafluoroethane), and CFC-115 (chloropentafluoroethane) in atmospheric and firn samples, we reconstruct records of their tropospheric histories spanning nearly 8 decades. These compounds were measured in polar firn air samples, in ambient air archived in canisters, and in situ at the AGAGE (Advanced Global Atmospheric Gases Experiment) network and affiliated sites. Global emissions to the atmosphere are derived from these observations using an inversion based on a 12-box atmospheric transport model. For CFC-13, we provide the first comprehensive global analysis. This compound increased monotonically from its first appearance in the atmosphere in the late 1950s to a mean global abundance of 3.18 ppt (dry-air mole fraction in parts per trillion, pmol mol(-1)) in 2016. Its growth rate has decreased since the mid-1980s but has remained at a surprisingly high mean level of 0.02 ppt yr(-1) since 2000, resulting in a continuing growth of CFC-13 in the atmosphere. Sigma CFC-114 increased from its appearance in the 1950s to a maximum of 16.6 ppt in the early 2000s and has since slightly declined to 16.3 ppt in 2016. CFC-115 increased monotonically from its first appearance in the 1960s and reached a global mean mole fraction of 8.49 ppt in 2016. Growth rates of all three compounds over the past years are significantly larger than would be expected from zero emissions. Under the assumption of unchanging lifetimes and atmospheric transport patterns, we derive global emissions from our measurements, which have remained unexpectedly high in recent years: mean yearly emissions for the last decade (2007-2016) of CFC-13 are at 0.48 +/- 0.15 kt yr(-1) (> 15% of past peak emissions), of 6 CFC-114 at 1.90 +/- 0.84 kt yr(-1) (similar to 10% of peak emissions), and of CFC-115 at 0.80 +/- 0.50 kt yr(-1) (> 5% of peak emissions). Mean yearly emissions of CFC-115 for 2015-2016 are 1.14 +/- 0.50 kt yr(-1) and have doubled compared to the 2007-2010 minimum. We find CFC-13 emissions from aluminum smelters but if extrapolated to global emissions, they cannot account for the lingering global emissions determined from the atmospheric observations. We find impurities of CFC-115 in the refrigerant HFC-125 (CHF2CF3) but if extrapolated to global emissions, they can neither account for the lingering global CFC-115 emissions determined from the atmospheric observations nor for their recent increases. We also conduct regional inversions for the years 2012-2016 for the northeastern Asian area using observations from the Korean AGAGE site at Gosan and find significant emissions for Sigma CFC-114 and CFC-115, suggesting that a large fraction of their global emissions currently occur in northeastern Asia and more specifically on the Chinese mainland.

2017
Meinshausen, M, Vogel E, Nauels A, Lorbacher K, Meinshausen N, Etheridge DM, Fraser PJ, Montzka SA, Rayner PJ, Trudinger CM, Krummel PB, Beyerle U, Canadell JG, Daniel JS, Enting IG, Law RM, Lunder CR, O'Doherty S, Prinn RG, Reimann S, Rubino M, Velders GJM, Vollmer MK, Wang RHJ, Weiss R.  2017.  Historical greenhouse gas concentrations for climate modelling (CMIP6). Geoscientific Model Development. 10:2057-2116.   10.5194/gmd-10-2057-2017   AbstractWebsite

Atmospheric greenhouse gas (GHG) concentrations are at unprecedented, record-high levels compared to the last 800 000 years. Those elevated GHG concentrations warm the planet and - partially offset by net cooling effects by aerosols - are largely responsible for the observed warming over the past 150 years. An accurate representation of GHG concentrations is hence important to understand and model recent climate change. So far, community efforts to create composite datasets of GHG concentrations with seasonal and latitudinal information have focused on marine boundary layer conditions and recent trends since the 1980s. Here, we provide consolidated datasets of historical atmospheric concentrations (mole fractions) of 43 GHGs to be used in the Climate Model Intercomparison Project Phase 6 (CMIP6) experiments. The presented datasets are based on AGAGE and NOAA networks, firn and ice core data, and archived air data, and a large set of published studies. In contrast to previous intercomparisons, the new datasets are latitudinally resolved and include seasonality. We focus on the period 1850-2014 for historical CMIP6 runs, but data are also provided for the last 2000 years. Weprovide consolidated datasets in various spatiotemporal resolutions for carbon dioxide (CO2), mcthanc (CH4) and nitrous oxide (N2O), as well as 40 other GHGs, namely 17 ozone-depleting substances, 11 hydrofluorocarbons (HFCs), 9 perfluorocarbons (PFCs), sulfur hexafluoride (SF6), nitrogen trifluoride (NF3) and sulfuryl fluoride (SO2F2). In addition we provide three equivalence species that aggregate concentrations of GHGs other than CO2, CH4 and N2O, weighted by their radiative forcing efficiencies. For the year 1850, which is used for pre-industrial control runs, we estimate annual global-mean surface concentrations of CO2 at 284.3 ppm, CH4 at 808.2 ppb and N2O at 273.0 ppb. The data are available at https://esgf-node.llnl.gov/search/input4mips/and www.climatecollege.unimelb.edu.au/cmip6. While the minimum CMIP6 recommendation is to use the global-and annual-mean time series, modelling groups can also choose our monthly and latitudinally resolved concentrations, which imply a stronger radiative forcing in the Northern Hemisphere winter (due to the latitudinal gradient and seasonality).

2014
Rigby, M, Prinn RG, O'Doherty S, Miller BR, Ivy D, Muhle J, Harth CM, Salameh PK, Arnold T, Weiss RF, Krummel PB, Steele LP, Fraser PJ, Young D, Simmonds PG.  2014.  Recent and future trends in synthetic greenhouse gas radiative forcing. Geophysical Research Letters. 41:2623-2630.   10.1002/2013gl059099   AbstractWebsite

Atmospheric measurements show that emissions of hydrofluorocarbons (HFCs) and hydrochlorofluorocarbons are now the primary drivers of the positive growth in synthetic greenhouse gas (SGHG) radiative forcing. We infer recent SGHG emissions and examine the impact of future emissions scenarios, with a particular focus on proposals to reduce HFC use under the Montreal Protocol. If these proposals are implemented, overall SGHG radiative forcing could peak at around 355mWm(-2) in 2020, before declining by approximately 26% by 2050, despite continued growth of fully fluorinated greenhouse gas emissions. Compared to no HFC policy projections, this amounts to a reduction in radiative forcing of between 50 and 240mWm(-2) by 2050 or a cumulative emissions saving equivalent to 0.5 to 2.8years of CO2 emissions at current levels. However, more complete reporting of global HFC emissions is required, as less than half of global emissions are currently accounted for.

Arnold, T, Ivy DJ, Harth CM, Vollmer MK, Muhle J, Salameh PK, Steele LP, Krummel PB, Wang RHJ, Young D, Lunder CR, Hermansen O, Rhee TS, Kim J, Reimann S, O'Doherty S, Fraser PJ, Simmonds PG, Prinn RG, Weiss RF.  2014.  HFC-43-10mee atmospheric abundances and global emission estimates. Geophysical Research Letters. 41:2228-2235.   10.1002/2013gl059143   AbstractWebsite

We report in situ atmospheric measurements of hydrofluorocarbon HFC-43-10mee (C5H2F10; 1,1,1,2,2,3,4,5,5,5-decafluoropentane) from seven observatories at various latitudes, together with measurements of archived air samples and recent Antarctic flask air samples. The global mean tropospheric abundance was 0.210.05ppt (parts per trillion, dry air mole fraction) in 2012, rising from 0.040.03ppt in 2000. We combine the measurements with a model and an inverse method to estimate rising global emissionsfrom 0.430.34Ggyr(-1) in 2000 to 1.130.31Ggyr(-1) in 2012 (similar to 1.9TgCO(2)-eqyr(-1) based on a 100year global warming potential of 1660). HFC-43-10meea cleaning solvent used in the electronics industryis currently a minor contributor to global radiative forcing relative to total HFCs; however, our calculated emissions highlight a significant difference from the available reported figures and projected estimates.

2011
Vollmer, MK, Miller BR, Rigby M, Reimann S, Muhle J, Krummel PB, O'Doherty S, Kim J, Rhee TS, Weiss RF, Fraser PJ, Simmonds PG, Salameh PK, Harth CM, Wang RHJ, Steele LP, Young D, Lunder CR, Hermansen O, Ivy D, Arnold T, Schmidbauer N, Kim KR, Greally BR, Hill M, Leist M, Wenger A, Prinn RG.  2011.  Atmospheric histories and global emissions of the anthropogenic hydrofluorocarbons HFC-365mfc, HFC-245fa, HFC-227ea, and HFC-236fa. Journal of Geophysical Research-Atmospheres. 116   10.1029/2010jd015309   AbstractWebsite

We report on ground-based atmospheric measurements and emission estimates of the four anthropogenic hydrofluorocarbons (HFCs) HFC-365mfc (CH(3)CF(2)CH(2)CF(3), 1,1,1,3,3-pentafluorobutane), HFC-245fa (CHF(2)CH(2)CF(3), 1,1,1,3,3-pentafluoropropane), HFC-227ea (CF(3)CHFCF(3), 1,1,1,2,3,3,3-heptafluoropropane), and HFC-236fa (CF(3)CH(2)CF(3), 1,1,1,3,3,3-hexafluoropropane). In situ measurements are from the global monitoring sites of the Advanced Global Atmospheric Gases Experiment (AGAGE), the System for Observations of Halogenated Greenhouse Gases in Europe (SOGE), and Gosan (South Korea). We include the first halocarbon flask sample measurements from the Antarctic research stations King Sejong and Troll. We also present measurements of archived air samples from both hemispheres back to the 1970s. We use a two-dimensional atmospheric transport model to simulate global atmospheric abundances and to estimate global emissions. HFC-365mfc and HFC-245fa first appeared in the atmosphere only similar to 1 decade ago; they have grown rapidly to globally averaged dry air mole fractions of 0.53 ppt (in parts per trillion, 10(-12)) and 1.1 ppt, respectively, by the end of 2010. In contrast, HFC-227ea first appeared in the global atmosphere in the 1980s and has since grown to similar to 0.58 ppt. We report the first measurements of HFC-236fa in the atmosphere. This long-lived compound was present in the atmosphere at only 0.074 ppt in 2010. All four substances exhibit yearly growth rates of >8% yr(-1) at the end of 2010. We find rapidly increasing emissions for the foam-blowing compounds HFC-365mfc and HFC-245fa starting in similar to 2002. After peaking in 2006 (HFC-365mfc: 3.2 kt yr(-1), HFC-245fa: 6.5 kt yr(-1)), emissions began to decline. Our results for these two compounds suggest that recent estimates from long-term projections (to the late 21st century) have strongly overestimated emissions for the early years of the projections (similar to 2005-2010). Global HFC-227ea and HFC-236fa emissions have grown to average values of 2.4 kt yr(-1) and 0.18 kt y(r-)1 over the 2008-2010 period, respectively.