Letter

Reversal of global atmospheric ethane and propane trends largely due to US oil and natural gas production

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Abstract

Non-methane hydrocarbons such as ethane are important precursors to tropospheric ozone and aerosols. Using data from a global surface network and atmospheric column observations we show that the steady decline in the ethane mole fraction that began in the 1970s1,2,3 halted between 2005 and 2010 in most of the Northern Hemisphere and has since reversed. We calculate a yearly increase in ethane emissions in the Northern Hemisphere of 0.42 (±0.19) Tg yr−1 between mid-2009 and mid-2014. The largest increases in ethane and the shorter-lived propane are seen over the central and eastern USA, with a spatial distribution that suggests North American oil and natural gas development as the primary source of increasing emissions. By including other co-emitted oil and natural gas non-methane hydrocarbons, we estimate a Northern Hemisphere total non-methane hydrocarbon yearly emission increase of 1.2 (±0.8) Tg yr−1. Atmospheric chemical transport modelling suggests that these emissions could augment summertime mean surface ozone by several nanomoles per mole near oil and natural gas production regions. Methane/ethane oil and natural gas emission ratios could suggest a significant increase in associated methane emissions; however, this increase is inconsistent with observed leak rates in production regions and changes in methane’s global isotopic ratio.

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Acknowledgements

This research would not have been possible without the contributions of many dedicated researchers that maintain the sampling programmes that provided the used data. The global VOC flask analyses are a component of NOAA’s Cooperative USA- and global-scale Greenhouse Gas Reference flask sampling network, which is supported in part by NOAA Climate Program Office’s AC4 Program. We greatly appreciate the work of many colleagues who have contributed to the programme operation and data processing, in particular C. Siso, P. Lang, J. Higgs, M. Crotwell, S. Wolter, D. Neff, J. Kofler, A. Andrews, B. Miller, D. Colegrove, C. Sweeney, E. Dlugokencky, and Y. Stenzel, and many unnamed CU Boulder undergraduate students who have processed the flask network data. The in situ monitoring at Summit is funded by the USA National Science Foundation, grant PLR-AON 1108391. We thank M. Fischer and S. Biraud for the operation of the STR and SGP site, respectively. The WGC and STR sites are operated with support from the California Energy Commission’s Natural Gas programme under USA Department of Energy Contract No. DE-AC02-05CH11231. Financial support for the measurements at JFJ is provided by the International Foundation High Altitude Research Stations JFJ and Gornergrat (HFSJG), and for the GC/MS measurements also by the Swiss Federal Office for the Environment (FOEN) in the Swiss National Program HALCLIM. In situ VOC measurements at Cape Verde are made with the assistance of L. Mendes, K. Read, and J. Hopkins. The University of York thanks NCAS and NERC for funding. The FTIR measurements at NIWA, Lauder, are core funded through New Zealand’s Ministry of Business, Innovation, and Employment. J.W.H. is supported by NASA under contract No. NNX13AH87G. The National Center for Atmospheric Research is supported by the USA National Science Foundation. The University of Liège contribution has been primarily supported by BELSPO and the F.R.S.—FNRS (Fonds de la Recherche Scientifique), both in Brussels. We thank P. Martinerie, at LGGE, Grenoble, France, for the reconstructed ethane firn air history in Fig. 1a. The global VOC monitoring is under the auspices of the World Meteorological Organization Global Atmospheric Watch (WMO-GAW) programme, which facilitates coordination between participating partners and quality control efforts. The VOC World Calibration Centre is funded by the German Umweltbundesamt. We also thank the staff of the World Data Centre for Greenhouse Gases at the Japan Meteorological Agency for the archiving and public posting of data used in this study.

Author information

Affiliations

  1. Institute of Arctic and Alpine Research, University of Colorado, Boulder, Colorado 80305, USA

    • Detlev Helmig
    • , Samuel Rossabi
    •  & Jacques Hueber
  2. Earth Systems Research Laboratory, National Oceanic and Atmospheric Administration, Boulder, Colorado 80305, USA

    • Pieter Tans
    • , Stephen A. Montzka
    • , Ken Masarie
    •  & Kirk Thoning
  3. Deutscher Wetterdienst, 82383 Hohenpeissenberg, Germany

    • Christian Plass-Duelmer
    •  & Anja Claude
  4. Wolfson Atmospheric Chemistry Laboratories, University of York, York YO10 5DD, UK

    • Lucy J. Carpenter
    •  & Shalini Punjabi
  5. National Centre for Atmospheric Science, University of York, York YO10 5DD, UK

    • Alastair C. Lewis
  6. Laboratory for Air Pollution and Environmental Technology, Empa, Swiss Federal Laboratories for Materials Science and Technology, 8600 Duebendorf, Switzerland

    • Stefan Reimann
    •  & Martin K. Vollmer
  7. Karlsruhe Institute for Technology, Campus Alpine, 82467 Garmisch-Partenkirchen, Germany

    • Rainer Steinbrecher
  8. National Center for Atmospheric Research, Boulder, Colorado 80301, USA

    • James W. Hannigan
    •  & Louisa K. Emmons
  9. Institute of Astrophysics and Geophysics, University of Liège, 4000 Liège, Belgium

    • Emmanuel Mahieu
    •  & Bruno Franco
  10. National Institute of Water and Atmospheric Research, Lauder 9352, New Zealand

    • Dan Smale
  11. Max Planck Institute for Chemistry, 55128 Mainz, Germany

    • Andrea Pozzer

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Contributions

D.H., study design, global flask network operation, Summit in situ measurements, data analyses, quality control, site comparisons, manuscript preparation. S.R., data processing, preparation of graphs, manuscript preparation. J.H., global flask network operation, analytical work, Summit in situ measurements. P.T., global flask network operation, manuscript preparation. S.A.M., propane data from the North American Tower flask programme and its quality control, manuscript preparation. K.M., NOAA network data management, NMHC global graphs shown in Fig. 2, manuscript preparation. K.T., data filtering, trend analyses, data statistics, manuscript preparation. C.P.-D., HPB NMHC monitoring, flask–in situ comparisons, manuscript preparation. A.C., HPB in situ NMHC monitoring. A.C.L., CVO NMHC in situ observations, manuscript preparation. L.J.C., CVO NMHC in situ observations, manuscript preparation. S.P., CVO NMHC in situ observations. S.R., JFJ NMHC in situ observations. M.K.V., JFJ NMHC in situ observations, manuscript preparation. R.S., VOC World Calibration Center, NMHC quality control, manuscript preparation. J.W.H., FTIR data evaluations and coordination, manuscript preparation. L.K.E., emissions modelling, ethane inventory data, manuscript preparation. E.M., JFJ FTIR data processing and analyses, manuscript preparation. B.F., JFJ FTIR data processing and analyses, manuscript preparation. D.S., Lauder FTIR observations and data processing, manuscript preparation. A.P., ethane inventory data, photochemical ozone modelling, manuscript preparation.

Competing interests

The authors declare no competing financial interests.

Corresponding author

Correspondence to Detlev Helmig.

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