Project Scientist

Research Interests:

  • AGAGE (Advanced Global Atmospheric Gases Experiment) http://agage.eas.gatech.edu/
  • Greenhouse gases
  • Halogenated trace gases
  • Ozone depleting compounds
  • Trace gas measurements (especially GC-FID/ECD/MSD)
  • Global warming
  • Top-down (measurement based) verification of bottom-up emission estimates
  • 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, Muhle J, Trudinger CM, Rigby M, Montzka SA, Harth CM, Miller BR, Henne S, Krummel PB, Hall BD, Young D, Kim J, Arduini J, Wenger A, Yao B, Reimann S, O'Doherty S, Maione M, Etheridge DM, Li SL, Verdonik DP, Park S, Dutton G, Steele LP, Lunder CR, Rhee TS, Hermansen O, Schmidbauer N, Wang RHJ, Hill M, Salameh PK, Langenfelds RL, Zhou LX, Blunier T, Schwander J, Elkins JW, Butler JH, Simmonds PG, Weiss RF, Prinn RG, Fraser PJ.  2016.  Atmospheric histories and global emissions of halons H-1211 (CBrClF2), H-1301 (CBrF3), and H-2402 (CBrF2CBrF2). Journal of Geophysical Research-Atmospheres. 121:3663-3686. AbstractWebsite

We report ground-based atmospheric measurements and emission estimates for the halons H-1211 (CBrClF2), H-1301 (CBrF3), and H-2402 (CBrF2CBrF2) from the AGAGE (Advanced Global Atmospheric Gases Experiment) and the National Oceanic and Atmospheric Administration global networks. We also include results from archived air samples in canisters and from polar firn in both hemispheres, thereby deriving an atmospheric record of nearly nine decades (1930s to present). All three halons were absent from the atmosphere until approximate to 1970, when their atmospheric burdens started to increase rapidly. In recent years H-1211 and H-2402 mole fractions have been declining, but H-1301 has continued to grow. High-frequency observations show continuing emissions of H-1211 and H-1301 near most AGAGE sites. For H-2402 the only emissions detected were derived from the region surrounding the Sea of Japan/East Sea. Based on our observations, we derive global emissions using two different inversion approaches. Emissions for H-1211 declined from a peak of 11ktyr(-1) (late 1990s) to 3.9ktyr(-1) at the end of our record (mean of 2013-2015), for H-1301 from 5.4ktyr(-1) (late 1980s) to 1.6ktyr(-1), and for H-2402 from 1.8ktyr(-1) (late 1980s) to 0.38ktyr(-1). Yearly summed halon emissions have decreased substantially; nevertheless, since 2000 they have accounted for approximate to 30% of the emissions of all major anthropogenic ozone depletion substances, when weighted by ozone depletion potentials.

Simmonds, PG, Rigby M, Manning AJ, Lunt MF, O'Doherty S, McCulloch A, Fraser PJ, Henne S, Vollmer MK, Mühle J, Weiss RF, Salameh PK, Young D, Reimann S, Wenger A, Arnold T, Harth CM, Krummel PB, Steele LP, Dunse BL, Miller BR, Lunder CR, Hermansen O, Schmidbauer N, Saito T, Yokouchi Y, Park S, Li S, Yao B, Zhou LX, Arduini J, Maione M, Wang RHJ, Ivy D, Prinn RG.  2016.  Global and regional emissions estimates of 1,1-difluoroethane (HFC-152a, CH3CHF2) from in situ and air archive observations. Atmospheric Chemistry and Physics. 16:365-382.: Copernicus Publications AbstractWebsite
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Chirkov, M, Stiller GP, Laeng A, Kellmann S, von Clarmann T, Boone CD, Elkins JW, Engel A, Glatthor N, Grabowski U, Harth CM, Kiefer M, Kolonjari F, Krummel PB, Linden A, Lunder CR, Miller BR, Montzka SA, Mühle J, O'Doherty S, Orphal J, Prinn RG, Toon G, Vollmer MK, Walker KA, Weiss RF, Wiegele A, Young D.  2016.  Global HCFC-22 measurements with MIPAS: retrieval, validation, global distribution and its evolution over 2005–2012. Atmospheric Chemistry and Physics. 16:3345-3368.: Copernicus Publications AbstractWebsite
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Simmonds, PG, Rigby M, Manning AJ, Lunt MF, O'Doherty S, McCulloch A, Fraser PJ, Henne S, Vollmer MK, Muhle J, Weiss RF, Salameh PK, Young D, Reimann S, Wenger A, Arnold T, Harth CM, Krummel PB, Steele LP, Dunse BL, Miller BR, Lunder CR, Hermansen O, Schmidbauer N, Saito T, Yokouchi Y, Park S, Li S, Yao B, Zhou LX, Arduini J, Maione M, Wang RHJ, Ivy D, Prinn RG.  2016.  Global and regional emissions estimates of 1,1-difluoroethane (HFC-152a, CH3CHF2) from in situ and air archive observations. Atmospheric Chemistry and Physics. 16:365-382. AbstractWebsite

High frequency, in situ observations from 11 globally distributed sites for the period 1994-2014 and archived air measurements dating from 1978 onward have been used to determine the global growth rate of 1,1-difluoroethane (HFC-152a, CH3CHF2). These observations have been combined with a range of atmospheric transport models to derive global emission estimates in a top-down approach. HFC-152a is a greenhouse gas with a short atmospheric lifetime of about 1.5 years. Since it does not contain chlorine or bromine, HFC-152a makes no direct contribution to the destruction of stratospheric ozone and is therefore used as a substitute for the ozone de- pleting chlorofluorocarbons (CFCs) and hydrochlorofluorocarbons (HCFCs). The concentration of HFC-152a has grown substantially since the first direct measurements in 1994, reaching a maximum annual global growth rate of 0.84 +/- 0.05 ppt yr(-1) in 2006, implying a substantial increase in emissions up to 2006. However, since 2007, the annual rate of growth has slowed to 0.38 +/- 0.04 ppt yr(-1) in 2010 with a further decline to an annual average rate of growth in 2013-2014 of -0.06 +/- 0.05 ppt yr(-1). The annual average Northern Hemisphere (NH) mole fraction in 1994 was 1.2 ppt rising to an annual average mole fraction of 10.1 ppt in 2014. Average annual mole fractions in the Southern Hemisphere (SH) in 1998 and 2014 were 0.84 and 4.5 ppt, respectively. We estimate global emissions of HFC-152a have risen from 7.3 +/- 5.6 Gg yr(-1) in 1994 to a maximum of 54.4 +/- 17.1 Gg yr(-1) in 2011, declining to 52.5 +/- 20.1 Gg yr(-1) in 2014 or 7.2 +/- 2.8 Tg-CO2 eq yr(-1). Analysis of mole fraction enhancements above regional background atmospheric levels suggests substantial emissions from North America, Asia, and Europe. Global HFC emissions (so called "bottom up" emissions) reported by the United Nations Framework Convention on Climate Change (UNFCCC) are based on cumulative national emission data reported to the UNFCCC, which in turn are based on national consumption data. There appears to be a significant underestimate (> 20 Gg) of "bottom-up" reported emissions of HFC-152a, possibly arising from largely underestimated USA emissions and undeclared Asian emissions.

Deeds, DA, Kulongoski JT, Mühle J, Weiss RF.  2015.  Tectonic activity as a significant source of crustal tetrafluoromethane emissions to the atmosphere: Observations in groundwaters along the San Andreas Fault. Earth and Planetary Science Letters. 412:163-172. AbstractWebsite

Abstract Tetrafluoromethane (CF4) concentrations were measured in 14 groundwater samples from the Cuyama Valley, Mil Potrero and Cuddy Valley aquifers along the Big Bend section of the San Andreas Fault System (SAFS) in California to assess whether tectonic activity in this region is a significant source of crustal CF4 to the atmosphere. Dissolved CF4 concentrations in all groundwater samples but one were elevated with respect to estimated recharge concentrations including entrainment of excess air during recharge ( C r e ; ∼30 fmol kg−1 H2O), indicating subsurface addition of CF4 to these groundwaters. Groundwaters in the Cuyama Valley contain small CF4 excesses (0.1–9 times C r e ), which may be attributed to an in situ release from weathering and a minor addition of deep crustal CF4 introduced to the shallow groundwater through nearby faults. CF4 excesses in groundwaters within 200 m of the SAFS are larger (10–980 times C r e ) and indicate the presence of a deep crustal flux of CF4 that is likely associated with the physical alteration of silicate minerals in the shear zone of the SAFS. Extrapolating CF4 flux rates observed in this study to the full extent of the SAFS (1300 km × 20–100 km) suggests that the SAFS potentially emits ( 0.3 – 1 ) × 10 − 1 kg CF4 yr−1 to the Earth's surface. For comparison, the chemical weathering of ∼ 7.5 × 10 4 km 2 of granitic rock in California is estimated to release ( 0.019 – 3.2 ) × 10 − 1 kg CF4 yr−1. Tectonic activity is likely an important, and potentially the dominant, driver of natural emissions of CF4 to the atmosphere. Variations in preindustrial atmospheric CF4 as observed in paleo-archives such as ice cores may therefore represent changes in both continental weathering and tectonic activity, including changes driven by variations in continental ice cover during glacial–interglacial transitions.

Dlugokencky, EJ, Hall BD, Montzka SA, Dutton G, Mühle J, Elkins JW.  2015.  [Global Climate, Atmospheric chemical composition] Long-lived greenhouse gases [in State of the Climate in 2014]. Bulletin of the American Meteorological Society. 96( Blunden J, Arndt DS, Eds.).:S39-S42. Abstract
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