Project Scientist

Research Interests

  • AGAGE (Advanced Global Atmospheric Gases Experiment)
  • 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


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

Recent Publications

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
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.

Zhang, G, Yao B, Vollmer MK, Montzka SA, Mühle J, Weiss RF, O'Doherty S, Li Y, Fang S, Reimann S.  2017.  Ambient mixing ratios of atmospheric halogenated compounds at five background stations in China. Atmospheric Environment. 160:55-69. AbstractWebsite

Abstract High precision measurements of three chlorofluorocarbons (CFCs), three hydrochlorofluorocarbons (HCFCs), six hydrofluorocarbons (HFCs), three perfluorocarbons (PFCs), and sulfur hexafluoride (SF6) were made at five Chinese background stations from January 2011 to December 2012. Their station means in the background air were 239.5 ± 0.69 parts-per-trillion dry-air mole fraction mixing ratios (ppt) for CFC-11, 536.5 ± 1.49 ppt for CFC-12, 74.66 ± 0.09 ppt for CFC-113, 232.1 ± 4.77 ppt for HCFC-22, 23.78 ± 0.29 ppt for HCFC-141b, 22.92 ± 0.42 ppt for HCFC-142b, 11.75 ± 0.43 ppt for HFC-125, 71.32 ± 1.35 ppt for HFC-134a, 13.62 ± 0.43 ppt for HFC-143a, 9.10 ± 1.26 ppt for HFC-152a, 25.45 ± 0.1 ppt for HFC-23, 7.28 ± 0.48 ppt for HFC-32, 4.32 ± 0.03 ppt for PFC-116, 0.63 ± 0.04 ppt for PFC-218, 1.36 ± 0.01 ppt for PFC-318, and 7.67 ± 0.03 ppt for SF6, respectively, which were comparable with those measured at the two Northern Hemisphere (NH) AGAGE stations: Mace Head, Ireland (MHD) and Trinidad Head, California, USA (THD). Compared with our results for earlier years from in-situ measurement at SDZ, background-air mixing ratios of CFCs are now declining, while those for HCFCs, HFCs, PFCs, and SF6 are still increasing. The ratios of the number of sampling events in which measured mixing ratios were elevated above background (pollution events) relative to the total sample frequency (POL/SUM) for CFCs, HCFCs, and HFCs were found to be station dependent, generally LAN > SDZ > LFS > XGL > WLG. The enhancement (△, polluted mixing ratios minus background mixing ratios) generally show distinct patterns, with HCFCs (40.7–175.4 ppt) > HFCs (15.8–66.3 ppt)> CFCs (15.8–33.8 ppt)> PFCs (0.1–0.9 ppt) at five stations, especially for HCFC-22 ranging from 36.9 ppt to 138.2 ppt. Combining with the molecular weights, our findings imply biggest emissions of HCFCs in the regions around these Chinese sites compared to HFCs and CFCs, while the smallest of PFCs, consistent with CFCs being phased out and replaced with HCFCs in China. In addition, relative emission strengths (emission was expressed by mole fractions) of these halocarbons in China were inferred as HCFC-22 > HCFC-141b > HFC-134a > HCFC-142b for the Yangtze River Delta (YRD) and as HCFC-22 > HCFC-142b > HCFC-141b ≈ HFC-134a in the North China Plain (NCP).

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
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
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.