Project Scientist

Research Interests

  • AGAGE (Advanced Global Atmospheric Gases Experiment) http://agage.mit.edu/ http://agage.eas.gatech.edu/
  • Global Warming, Climate Change, Greenhouse Gases (GHGs)
  • Stratospheric Ozone Depletion, Ozone Depleting Substances (ODSs)
  • Global and regional emissions, loss processes, and lifetimes of ODSs and GHGs
  • Top-down (measurement based) verification of bottom-up emission estimates
  • Top-down (measurement based) verification of compliance with the Montreal Protocol on Substances that Deplete the Ozone Layer and the Paris Agreement
  • Halogenated trace gases
  • Perfluorinated Compounds (PFCs) and their emissions from global aluminium, rare-earth, and semi-conductor industries
  • Trace gas measurement techniques (GC-FID/ECD, GC/MSD, GC/TOF-MS, PTR-TOF-MS, CRDS)
  • Atmospheric chemistry
  • Wildfire emissions
  • Long-range transport of pollutants

Degrees

  • Diploma in Chemistry, University of Wuppertal
  • Doctor of Natural Sciences, Max Planck Institute for Chemistry, Mainz and Johannes Gutenberg University Mainz

Recent Publications

Vollmer, MK, Young D, Trudinger CM, Mühle 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 L, Fraser PJ, Prinn RG, Weiss RF, Simmonds PG.  2018.  Atmospheric histories and emissions of chlorofluorocarbons CFC-13 (CClF3), ΣCFC-114 (C2Cl2F4), and CFC-115 (C2ClF5). Atmospheric Chemistry and Physics. 18:979-1002.: Copernicus Publications AbstractWebsite
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Simmonds, PG, Rigby M, McCulloch A, Vollmer MK, Henne S, Mühle J, O'Doherty S, Manning AJ, Krummel PB, Fraser PJ, Young D, Weiss RF, Salameh PK, Harth CM, Reimann S, Trudinger CM, Steele P, 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.: Copernicus Publications 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 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 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  ∼  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.

Li, S, Park S, Park MK, Jo CO, Park S, Lee JY, Ha KJ, Oh H, Lee JY, Ha KJ, Oh H, Mühle J, Weiss RF, Kim KR, Montzka SA, Miller BR, Moore F, O'Doherty S, Krummel PB, Atlas E, Miller BR, Moore F, Wofsy SC.  2018.  Chemical evidence of inter-hemispheric air mass intrusion into the Northern Hemisphere mid-latitudes. Scientific Reports. 8:4669. Abstract

The East Asian Summer Monsoon driven by temperature and moisture gradients between the Asian continent and the Pacific Ocean, leads to approximately 50% of the annual rainfall in the region across 20-40°N. Due to its increasing scientific and social importance, there have been several previous studies on identification of moisture sources for summer monsoon rainfall over East Asia mainly using Lagrangian or Eulerian atmospheric water vapor models. The major source regions for EASM previously proposed include the North Indian Ocean, South China Sea and North western Pacific. Based on high-precision and high-frequency 6-year measurement records of hydrofluorocarbons (HFCs), here we report a direct evidence of rapid intrusion of warm and moist tropical air mass from the Southern Hemisphere (SH) reaching within a couple of days up to 33°N into East Asia. We further suggest that the combination of direct chemical tracer record and a back-trajectory model with physical meteorological variables helps pave the way to identify moisture sources for monsoon rainfall. A case study for Gosan station (33.25°N, 126.19°E) indicates that the meridional transport of precipitable water from the SH accompanying the southerly/southwesterly flow contributes most significantly to its summer rainfall.[on SciFinder (R)]

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 S, Loh ZM, Lunder CR, Maione M, Manning AJ, Miller BR, Mitrevski B, Mühle 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 L.  2018.  History of chemically and radiatively important atmospheric gases from the Advanced Global Atmospheric Gases Experiment (AGAGE). Earth Syst. Sci. Data. 10:985-1018.: Copernicus Publications AbstractWebsite
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Park, S, Li S, Mühle J, O'Doherty S, Weiss RF, Fang X, Reimann S, Prinn RG.  2018.  Toward resolving the budget discrepancy of ozone-depleting carbon tetrachloride (CCl4): an analysis of top-down emissions from China. Atmospheric Chemistry and Physics. 18:11729-11738.: Copernicus Publications AbstractWebsite
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Arnold, T, Manning AJ, Kim J, Li S, Webster H, Thomson D, Mühle 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.: Copernicus Publications AbstractWebsite
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Lunt, MF, Park S, Li S, Henne S, Manning AJ, Ganesan AL, Simpson IJ, Blake DR, Liang Q, O'Doherty S, Harth CM, Mühle J, Salameh PK, Weiss RF, Krummel PB, Fraser PJ, Prinn RG, Reimann S, Rigby M.  2018.  Continued Emissions of the Ozone-Depleting Substance Carbon Tetrachloride From Eastern Asia. Geophysical Research Letters. 45:11,423-11,430. AbstractWebsite

Abstract Carbon tetrachloride (CCl4) is an ozone-depleting substance, accounting for about 10% of the chlorine in the troposphere. Under the terms of the Montreal Protocol, its production for dispersive uses was banned from 2010. In this work we show that, despite the controls on production being introduced, CCl4 emissions from the eastern part of China did not decline between 2009 and 2016. This finding is in contrast to a recent bottom-up estimate, which predicted a significant decrease in emissions after the introduction of production controls. We find eastern Asian emissions of CCl4 to be 16 (9–24) Gg/year on average between 2009 and 2016, with the primary source regions being in eastern China. The spatial distribution of emissions that we derive suggests that the source distribution of CCl4 in China changed during the 8-year study period, indicating a new source or sources of emissions from China's Shandong province after 2012.

Leedham Elvidge, E, Bönisch H, Brenninkmeijer CAM, Engel A, Fraser PJ, Gallacher E, Langenfelds R, Mühle J, Oram DE, Ray EA, Ridley AR, Röckmann 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 facto. Atmospheric Chemistry and Physics. 18:3369-3385.: Copernicus Publications 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 andC3F8 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 resultsshowed 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 Universityof 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 meanages 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, O'Doherty S, Young D, Mühle J, Krummel PB, Steele P, Fraser PJ, Manning AJ, Weiss RF, Salameh PK, Harth CM, Wang RHJ, Prinn RG.  2017.  Changing trends and emissions of hydrochlorofluorocarbons (HCFCs) and their hydrofluorocarbon (HFCs) replacements. Atmospheric Chemistry and Physics. 17:4641-4655.: Copernicus Publications AbstractWebsite
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Rigby, M, Montzka SA, Prinn RG, White JWC, Young D, O’Doherty S, Lunt MF, Ganesan AL, Manning AJ, Simmonds PG, Salameh PK, Harth CM, Mühle J, Weiss RF, Fraser PJ, Steele PL, Krummel PB, McCulloch A, Park S.  2017.  Role of atmospheric oxidation in recent methane growth. Proceedings of the National Academy of Sciences. AbstractWebsite

The growth in global methane (CH4) concentration, which had been ongoing since the industrial revolution, stalled around the year 2000 before resuming globally in 2007. We evaluate the role of the hydroxyl radical (OH), the major CH4 sink, in the recent CH4 growth. We also examine the influence of systematic uncertainties in OH concentrations on CH4 emissions inferred from atmospheric observations. We use observations of 1,1,1-trichloroethane (CH3CCl3), which is lost primarily through reaction with OH, to estimate OH levels as well as CH3CC3 emissions, which have uncertainty that previously limited the accuracy of OH estimates. We find a 64–70% probability that a decline in OH has contributed to the post-2007 methane rise. Our median solution suggests that CH4 emissions increased relatively steadily during the late 1990s and early 2000s, after which growth was more modest. This solution obviates the need for a sudden statistically significant change in total CH4 emissions around the year 2007 to explain the atmospheric observations and can explain some of the decline in the atmospheric 13CH4/12CH4 ratio and the recent growth in C2H6. Our approach indicates that significant OH-related uncertainties in the CH4 budget remain, and we find that it is not possible to implicate, with a high degree of confidence, rapid global CH4 emissions changes as the primary driver of recent trends when our inferred OH trends and these uncertainties are considered.