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.

Access optionsAccess options

Rent or Buy article

Get time limited or full article access on ReadCube.


All prices are NET prices.


  1. 1.

    et al. Recent decreases in fossil-fuel emissions of ethane and methane derived from firn air. Nature 476, 198–201 (2011).

  2. 2.

    et al. Evidence from firn air for recent decreases in non-methane hydrocarbons and a 20th century increase in nitrogen oxides in the northern hemisphere. Atmos. Environ. 54, 592–602 (2012).

  3. 3.

    et al. Reconstruction of Northern Hemisphere 1950–2010 atmospheric non-methane hydrocarbons. Atmos. Chem. Phys. 14, 1463–1483 (2014).

  4. 4.

    , , & Preindustrial atmospheric ethane levels inferred from polar ice cores: a constraint on the geologic sources of atmospheric ethane and methane. Geophys. Res. Lett. 43, 214–221 (2015).

  5. 5.

    , & Global comparison of VOC and CO observations in urban areas. Atmos. Environ. 44, 5053–5064 (2010).

  6. 6.

    et al. Multiyear trends in volatile organic compounds in Los Angeles, California: five decades of decreasing emissions. J. Geophys. Res. 117, D00V17 (2012).

  7. 7.

    et al. Long-term decline of global atmospheric ethane concentrations and implications for methane. Nature 488, 490–494 (2012).

  8. 8.

    et al. Seasonal variability of atmospheric nitrogen oxides and non-methane hydrocarbons at the GEOSummit station, Greenland. Atmos. Chem. Phys. 12, 6827–6849 (2015).

  9. 9.

    , , & C2–C8 hydrocarbon measurement and quality control procedures at the Global Atmosphere Watch Observatory Hohenpeissenberg. J. Chrom. 953, 175–197 (2002).

  10. 10.

    et al. Intra-annual cycles of NMVOC in the tropical marine boundary layer and their use for interpreting seasonal variability in CO. J. Geophys. Res. 114, D21303 (2009).

  11. 11.

    et al. Can positive matrix factorization help to understand patterns of organic trace gases at the continental Global Atmosphere Watch site Hohenpeissenberg? Atmos. Chem. Phys. 15, 1221–1236 (2015).

  12. 12.

    et al. Retrieval of ethane from ground-based FTIR solar spectra using improved spectroscopy: recent burden increase above Jungfraujoch. J. Quant. Spec. Radiat. Trans. 160, 36–49 (2015).

  13. 13.

    et al. Hydrocarbon emissions characterization in the Colorado Front Range: a pilot study. J. Geophys. Res. 117, 1–19 (2012).

  14. 14.

    et al. Highly elevated atmospheric levels of volatile organic compounds in the Uintah Basin, Utah. Environ. Sci. Technol. 48, 4707–4715 (2014).

  15. 15.

    , & Influence of oil and gas emissions on ambient atmospheric non-methane hydrocarbons in residential areas of Northeastern Colorado. Elementa 2, 1–16 (2014).

  16. 16.

    et al. Impact of marcellus shale natural gas development in southwest Pennsylvania on volatile organic compound emissions and regional air quality. Environ. Sci. Technol. 49, 3175–3184 (2015).

  17. 17.

    et al. Methane emissions estimate from airborne measurements over a western United States natural gas field. Geophys. Res. Lett. 40, 4393–4397 (2013).

  18. 18.

    et al. Rapid photochemical production of ozone at high concentrations in a rural site during winter. Nature Geosci. 2, 120–122 (2009).

  19. 19.

    et al. Anatomy of wintertime ozone associated with oil and natural gas extraction activity in Wyoming and Utah. Elementa 2, 1–15 (2014).

  20. 20.

    et al. Regional air quality impacts of hydraulic fracturing and shale natural gas activity: evidence from ambient VOC observations. Atmos. Environ. 110, 144–150 (2015).

  21. 21.

    & Is the shale boom reversing progress in curbing ozone pollution? EOS 96, (2015).

  22. 22.

    US Greenhouse Gas Inventory (EPA, accessed 4 April, 2016);

  23. 23.

    et al. Three decades of global methane sources and sinks. Nature Geosci. 6, 813–823 (2013).

  24. 24.

    et al. Evaluating ethane and methane emissions associated with the development of oil and natural gas extraction in North America. Environ. Res. Lett. 11, 044010 (2016).

  25. 25.

    , & Contribution of oil and natural gas production to renewed increase of atmospheric methane (2007–2014): top-down estimate from ethane and methane column observations. Atmos. Chem. Phys. 16, 3227–3244 (2016).

  26. 26.

    et al. A large increase in US methane emissions over the past decade inferred from satellite data and surface observations. Geophys. Res. Lett. 43, 2218–2224 (2016).

  27. 27.

    et al. A 21st century shift from fossil-fuel to biogenic methane emissions indicated by 13CH4. Science (2016).

  28. 28.

    et al. Quantifying atmospheric methane emissions from the Haynesville, Fayetteville, and northeastern Marcellus shale gas production regions. J. Geophys. Res. 120, 2119–2139 (2015).

  29. 29.

    et al. Aircraft-based estimate of total methane emissions from the Barnett Shale region. Environ. Sci. Technol. 49, 8124–8131 (2015).

  30. 30.

    et al. A new look at methane and nonmethane hydrocarbon emissions from oil and natural gas operations in the Colorado Denver-Julesburg Basin. J. Geophys. Res. 119, 6836–6852 (2014).

  31. 31.

    et al. Sampling, storage, and analysis of C2–C7 non-methane hydrocarbons from the US National Oceanic and Atmospheric Administration Cooperative Air Sampling Network glass flasks. J. Chromatogr. A 1188, 75–87 (2008).

  32. 32.

    et al. Volatile organic compounds in the global atmosphere. Eos Trans. AGU 90, 513–514 (2009).

  33. 33.

    World Calibration Centre for Volatile Organic Compounds (WCC-VOC) (Karlsruhe Institute of Technology, accessed 14 April 2016);

  34. 34.

    A WMO/GAW Expert Workshop on Global Long-Term Measurements of Volatile Organic Compounds (VOCs) Report No. 171 36 (WMO, 2007).

  35. 35.

    , , , & Evaluation of solid adsorbent materials for cryogen-free trapping—gas chromatographic analysis of atmospheric C2–C6 non-methane hydrocarbons. J. Chromatogr. A 1134, 1–15 (2006).

  36. 36.

    Global Atmospheric VOC Monitoring Program (Atmospheric Research Laboratory, Institute of Arctic and Alpine Research, University of Colorado, accessed 31 March 2016);

  37. 37.

    , , & Seasonal behavior of non-methane hydrocarbons in the firn air at Summit, Greenland. Atmos. Environ. 85, 234–246 (2014).

  38. 38.

    et al. Medusa: a sample preconcentration and GC/MS detector system for in situ measurements of atmospheric trace halocarbons, hydrocarbons, and sulfur compounds. Anal. Chem. 80, 1536–1545 (2008).

  39. 39.

    et al. International comparison of a hydrocarbon gas standard at the picomol per mol level. Anal. Chem. 86, 2580–2589 (2014).

  40. 40.

    , & Atmospheric carbon-dioxide at Mauna Loa observatory.2. analysis of the NOAA GMCC data, 1974–1985. J. Geophys. Res. 94, 8549–8565 (1989).

  41. 41.

    , & Power of the Mann-Kendall and Spearman’s rho tests for detecting monotonic trends in hydrological series. J. Hydrol. 259, 254–271 (2002).

  42. 42.

    & Extension and integration of atmospheric carbon-dioxide data into a globally consistent measurement record. J. Geophys. Res. 100, 11593–11610 (1995).

  43. 43.

    GLOBALVIEW (NOAA Earth System Research Laboratory Global Monitoring Division, accessed 4 April 2016),

  44. 44.

    , & Latitudinal distribution of the sources and sinks of atmospheric carbon-dioxide derived from surface observations and an atmospheric transport model. J. Geophys. Res. 94, 5151–5172 (1989).

  45. 45.

    et al. Multiyear infrared solar spectroscopic measurements of HCN, CO, C2H6, and C2H2 tropospheric columns above Lauder, New Zealand (45 °S latitude). J. Geophys. Res. 107, ACH 1-1–ACH 1-12 (2002).

  46. 46.

    et al. Trends and variations in CO, C2H6, and HCN in the Southern Hemisphere point to the declining anthropogenic emissions of CO and C2H6. Atmos. Chem. Phys. 12, 7543–7555 (2012).

  47. 47.

    et al. Trend analysis of greenhouse gases over Europe measured by a network of ground-based remote FTIR instruments. Atmos. Chem. Phys. 8, 6719–6727 (2008).

  48. 48.

    et al. HTAP_v2: a mosaic of regional and global emission gridmaps for 2008 and 2010 to study hemispheric transport of air pollution. Atmos. Chem. Phys. 15, 12867–12909 (2015).

  49. 49.

    et al. The Model of Emissions of Gases and Aerosols from Nature version 2.1 (MEGAN2.1): an extended and updated framework for modeling biogenic emissions. Geosci. Model Dev. 5, 1471–1492 (2012).

  50. 50.

    et al. The Fire INventory from NCAR (FINN): a high resolution global model to estimate the emissions from open burning. Geosci. Model Dev. 4, 625–641 (2011).

  51. 51.

    , & Scenarios of long-term socio-economic and environmental development under climate stabilization. Technol. Forecast. Soc. Change 74, 887–935 (2007).

  52. 52.

    et al. AOD trends during 2001–2010 from observations and model simulations. Atmos. Chem. Phys. 15, 5521–5535 (2015).

  53. 53.

    , , , & Volatile organic compound distributions during the NACHTT campaign at the Boulder Atmospheric Observatory: influence of urban and natural gas sources. J. Geophys. Res. 118, 10614–10637 (2013).

  54. 54.

    et al. Development cycle 2 of the modular earth submodel system (MESSy2). Geosci. Model Dev. 3, 717–752 (2010).

  55. 55.

    et al. Observed and simulated global distribution and budget of atmospheric C2-C5 alkanes. Atmos. Chem. Phys. 10, 4403–4422 (2010).

Download references


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


  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


  1. Search for Detlev Helmig in:

  2. Search for Samuel Rossabi in:

  3. Search for Jacques Hueber in:

  4. Search for Pieter Tans in:

  5. Search for Stephen A. Montzka in:

  6. Search for Ken Masarie in:

  7. Search for Kirk Thoning in:

  8. Search for Christian Plass-Duelmer in:

  9. Search for Anja Claude in:

  10. Search for Lucy J. Carpenter in:

  11. Search for Alastair C. Lewis in:

  12. Search for Shalini Punjabi in:

  13. Search for Stefan Reimann in:

  14. Search for Martin K. Vollmer in:

  15. Search for Rainer Steinbrecher in:

  16. Search for James W. Hannigan in:

  17. Search for Louisa K. Emmons in:

  18. Search for Emmanuel Mahieu in:

  19. Search for Bruno Franco in:

  20. Search for Dan Smale in:

  21. Search for Andrea Pozzer in:


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.

Supplementary information

PDF files

  1. 1.

    Supplementary Information

    Supplementary Information

About this article

Publication history






Further reading