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

Hossaini, R, Atlas E, Dhomse SS, Chipperfield MP, Bernath PF, Fernando AM, Mühle J, Leeson AA, Montzka SA, Feng W, Harrison JJ, Krummel P, Vollmer MK, Reimann S, O'Doherty S, Young D, Maione M, Arduini J, Lunder CR.  2019.  Recent Trends in Stratospheric Chlorine from Very Short-Lived Substances. Journal of Geophysical Research: Atmospheres. 124   10.1029/2018JD029400   AbstractWebsite

Abstract Very short-lived substances (VSLS), including dichloromethane (CH2Cl2), chloroform (CHCl3), perchloroethylene (C2Cl4) and 1,2-dichloroethane (C2H4Cl2), are a stratospheric chlorine source and therefore contribute to ozone depletion. We quantify stratospheric chlorine trends from these VSLS (VSLCltot) using a chemical transport model and atmospheric measurements, including novel high-altitude aircraft data from the NASA VIRGAS (2015) and POSIDON (2016) missions. We estimate VSLCltot increased from 69 (±14) ppt Cl in 2000 to 111 (±22) ppt Cl in 2017, with >80% delivered to the stratosphere through source gas injection (SGI), and the remainder from product gases. The modelled evolution of chlorine SGI agrees well with historical aircraft data, which corroborate reported surface CH2Cl2 increases since the mid-2000s. The relative contribution of VSLS to total stratospheric chlorine increased from ~2% in 2000 to ~3.4% in 2017, reflecting both VSLS growth and decreases in long-lived halocarbons. We derive a mean VSLCltot growth rate of 3.8 (±0.3) ppt Cl/yr between 2004-2017, though year-to-year growth rates are variable and were small or negative in the period 2015-2017. Whether this is a transient effect, or longer-term stabilization, requires monitoring. In the upper stratosphere, the modelled rate of HCl decline (2004-2017) is -5.2 %/decade with VSLS included, in good agreement to ACE satellite data (-4.8 %/decade), and 15% slower than a model simulation without VSLS. Thus, VSLS have offset a portion of stratospheric chlorine reductions since the mid-2000s.

Li, PY, Muhle J, Montzka SA, Oram DE, Miller BR, Weiss RF, Fraser PJ, Tanhua T.  2019.  Atmospheric histories, growth rates and solubilities in seawater and other natural waters of the potential transient tracers HCFC-22, HCFC-141b, HCFC-142b, HFC-134a, HFC-125, HFC-23, PFC-14 and PFC-116. Ocean Science. 15:33-60.   10.5194/os-15-33-2019   AbstractWebsite

We present consistent annual mean atmospheric histories and growth rates for the mainly anthropogenic halogenated compounds HCFC-22, HCFC-141b, HCFC-142b, HFC-134a, HFC-125, HFC-23, PFC-14 and PFC-116, which are all potentially useful oceanic transient tracers (tracers of water transport within the ocean), for the Northern and Southern Hemisphere with the aim of providing input histories of these compounds for the equilibrium between the atmosphere and surface ocean. We use observations of these halogenated compounds made by the Advanced Global Atmospheric Gases Experiment (AGAGE), the Scripps Institution of Oceanography (SIO), the Commonwealth Scientific and Industrial Research Organization (CSIRO), the National Oceanic and Atmospheric Administration (NOAA) and the University of East Anglia (UEA). Prior to the direct observational record, we use archived air measurements, firn air measurements and published model calculations to estimate the atmospheric mole fraction histories. The results show that the atmospheric mole fractions for each species, except HCFC-14 lb and HCFC-142b, have been increasing since they were initially produced. Recently, the atmospheric growth rates have been decreasing for the HCFCs (HCFC-22, HCFC-141b and HCFC-142b), increasing for the HFCs (HFC-134a, HFC-125, HFC-23) and stable with little fluctuation for the PFCs (PFC-14 and PFC-116) investigated here. The atmospheric histories (source functions) and natural background mole fractions show that HCFC-22, HCFC-141b, HCFC-142b, HFC-134a, HFC-125 and HFC-23 have the potential to be oceanic transient tracers for the next few decades only because of the recently imposed bans on production and consumption. When the atmospheric histories of the compounds are not monotonically changing, the equilibrium atmospheric mole fraction (and ultimately the age associated with that mole fraction) calculated from their concentration in the ocean is not unique, reducing their potential as transient tracers. Moreover, HFCs have potential to be oceanic transient tracers for a longer period in the future than HCFCs as the growth rates of HFCs are increasing and those of HCFCs are decreasing in the background atmosphere. PFC-14 and PFC-116, however, have the potential to be tracers for longer periods into the future due to their extremely long lifetimes, steady atmospheric growth rates and no explicit ban on their emissions. In this work, we also derive solubility functions for HCFC-22, HCFC-14 lb, HCFC-142b, HFC-134a, HFC-125, HFC-23, PFC-14 and PFC-116 in water and seawater to facilitate their use as oceanic transient tracers. These functions are based on the Clark-Glew-Weiss (CGW) water solubility function fit and salting-out coefficients estimated by the poly-parameter linear free-energy relationships (pp-LFERs). Here we also provide three methods of seawater solubility estimation for more compounds. Even though our intention is for application in oceanic research, the work described in this paper is potentially useful for tracer studies in a wide range of natural waters, including freshwater and saline lakes, and, for the more stable compounds, groundwaters.

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.

Rigby, M, Park S, Saito T, Western LM, Redington AL, Fang X, Henne S, Manning AJ, Prinn RG, Dutton GS, Fraser PJ, Ganesan AL, Hall BD, Harth CM, Kim J, Kim KR, Krummel PB, Lee T, Li S, Liang Q, Lunt MF, Montzka SA, Mühle J, O’Doherty S, Park MK, Reimann S, Salameh PK, Simmonds P, Tunnicliffe RL, Weiss RF, Yokouchi Y, Young D.  2019.  Increase in CFC-11 emissions from eastern China based on atmospheric observations. Nature. 569:546-550.   10.1038/s41586-019-1193-4   AbstractWebsite

The recovery of the stratospheric ozone layer relies on the continued decline in the atmospheric concentrations of ozone-depleting gases such as chlorofluorocarbons1. The atmospheric concentration of trichlorofluoromethane (CFC-11), the second-most abundant chlorofluorocarbon, has declined substantially since the mid-1990s2. A recently reported slowdown in the decline of the atmospheric concentration of CFC-11 after 2012, however, suggests that global emissions have increased3,4. A concurrent increase in CFC-11 emissions from eastern Asia contributes to the global emission increase, but the location and magnitude of this regional source are unknown3. Here, using high-frequency atmospheric observations from Gosan, South Korea, and Hateruma, Japan, together with global monitoring data and atmospheric chemical transport model simulations, we investigate regional CFC-11 emissions from eastern Asia. We show that emissions from eastern mainland China are 7.0 ± 3.0 (±1 standard deviation) gigagrams per year higher in 2014–2017 than in 2008–2012, and that the increase in emissions arises primarily around the northeastern provinces of Shandong and Hebei. This increase accounts for a substantial fraction (at least 40 to 60 per cent) of the global rise in CFC-11 emissions. We find no evidence for a significant increase in CFC-11 emissions from any other eastern Asian countries or other regions of the world where there are available data for the detection of regional emissions. The attribution of any remaining fraction of the global CFC-11 emission rise to other regions is limited by the sparsity of long-term measurements of sufficient frequency near potentially emissive regions. Several considerations suggest that the increase in CFC-11 emissions from eastern mainland China is likely to be the result of new production and use, which is inconsistent with the Montreal Protocol agreement to phase out global chlorofluorocarbon production by 2010.

Fang, X, Park S, Saito T, Tunnicliffe R, Ganesan AL, Rigby M, Li S, Yokouchi Y, Fraser PJ, Harth CM, Krummel PB, Mühle J, O’Doherty S, Salameh PK, Simmonds PG, Weiss RF, Young D, Lunt MF, Manning AJ, Gressent A, Prinn RG.  2018.  Rapid increase in ozone-depleting chloroform emissions from China. Nature Geoscience. 12:89-93.   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.

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   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 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.

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   10.5194/acp-18-979-2018   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   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 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.   10.1038/s41598-018-22266-0   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   10.5194/essd-10-985-2018   AbstractWebsite
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