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Preindustrial 14CH4 indicates greater anthropogenic fossil CH4 emissions


Atmospheric methane (CH4) is a potent greenhouse gas, and its mole fraction has more than doubled since the preindustrial era1. Fossil fuel extraction and use are among the largest anthropogenic sources of CH4 emissions, but the precise magnitude of these contributions is a subject of debate2,3. Carbon-14 in CH4 (14CH4) can be used to distinguish between fossil (14C-free) CH4 emissions and contemporaneous biogenic sources; however, poorly constrained direct 14CH4 emissions from nuclear reactors have complicated this approach since the middle of the 20th century4,5. Moreover, the partitioning of total fossil CH4 emissions (presently 172 to 195 teragrams CH4 per year)2,3 between anthropogenic and natural geological sources (such as seeps and mud volcanoes) is under debate; emission inventories suggest that the latter account for about 40 to 60 teragrams CH4 per year6,7. Geological emissions were less than 15.4 teragrams CH4 per year at the end of the Pleistocene, about 11,600 years ago8, but that period is an imperfect analogue for present-day emissions owing to the large terrestrial ice sheet cover, lower sea level and extensive permafrost. Here we use preindustrial-era ice core 14CH4 measurements to show that natural geological CH4 emissions to the atmosphere were about 1.6 teragrams CH4 per year, with a maximum of 5.4 teragrams CH4 per year (95 per cent confidence limit)—an order of magnitude lower than the currently used estimates. This result indicates that anthropogenic fossil CH4 emissions are underestimated by about 38 to 58 teragrams CH4 per year, or about 25 to 40 per cent of recent estimates. Our record highlights the human impact on the atmosphere and climate, provides a firm target for inventories of the global CH4 budget, and will help to inform strategies for targeted emission reductions9,10.

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Fig. 1: Reconstruction of atmospheric 14CH4 from firn air and ice core data.
Fig. 2: Growth in fossil CH4 emissions and fossil fuel consumption.

Data availability

The ice core and firn air 14CH4 data presented in Fig. 1 are provided in Supplementary Information Tables 2, 6. Additional measurements not provided in Supplementary Information Tables 18 are available via the NSF Arctic Data Center at

Code availability

The code for the firn air inverse model and atmospheric box model (MATLAB) is available from the corresponding author upon request.


  1. 1.

    Meinshausen, M. et al. Historical greenhouse gas concentrations for climate modelling (CMIP6). Geosci. Model Dev. 10, 2057–2116 (2017).

    CAS  Article  ADS  Google Scholar 

  2. 2.

    Saunois, M. et al. The global methane budget 2000–2012. Earth Syst. Sci. Data 8, 697–751 (2016).

    Google Scholar 

  3. 3.

    Schwietzke, S. et al. Upward revision of global fossil fuel methane emissions based on isotope database. Nature 538, 88–91 (2016); corrigendum 543, 452 (2017).

    CAS  Article  ADS  Google Scholar 

  4. 4.

    Lassey, K. R., Etheridge, D. M., Lowe, D. C., Smith, A. M. & Ferretti, D. F. Centennial evolution of the atmospheric methane budget: what do the carbon isotopes tell us? Atmos. Chem. Phys. 7, 2119–2139 (2007).

    CAS  Article  ADS  Google Scholar 

  5. 5.

    Zazzeri, G., Acuña Yeomans, E. & Graven, H. D. Global and regional emissions of radiocarbon from nuclear power plants from 1972 to 2016. Radiocarbon 60, 1067–1081 (2018).

    CAS  Article  Google Scholar 

  6. 6.

    Etiope, G. Natural Gas Seepage: The Earth's Hydrocarbon Degassing Vol. 1 (Springer International Publishing, 2015).

  7. 7.

    Etiope, G., Ciotoli, G., Schwietzke, S. & Schoell, M. Gridded maps of geological methane emissions and their isotopic signature. Earth Syst. Sci. Data 11, 1–22 (2019).

    Google Scholar 

  8. 8.

    Petrenko, V. V. et al. Minimal geological methane emissions during the Younger Dryas–Preboreal abrupt warming event. Nature 548, 443–446 (2017).

    CAS  Article  ADS  Google Scholar 

  9. 9.

    Höglund-Isaksson, L. Global anthropogenic methane emissions 2005–2030: technical mitigation potentials and costs. Atmos. Chem. Phys. 12, 9079–9096 (2012).

    Article  ADS  Google Scholar 

  10. 10.

    Howarth, R. W. Methane emissions and climatic warming risk from hydraulic fracturing and shale gas development: implications for policy. Eng. Emis. Con. Tech. 3, 45–54 (2015).

    Google Scholar 

  11. 11.

    Nicewonger, M. R., Aydin, M., Prather, M. J. & Saltzman, E. S. Large changes in biomass burning over the last millennium inferred from paleoatmospheric ethane in polar ice cores. Proc. Natl Acad. Sci. USA 115, 12413–12418 (2018).

    CAS  Article  ADS  Google Scholar 

  12. 12.

    Bock, M. et al. Glacial/interglacial wetland, biomass burning, and geologic methane emissions constrained by dual stable isotopic CH4 ice core records. Proc. Natl Acad. Sci. USA 114, E5778–E5786 (2017).

    CAS  Article  Google Scholar 

  13. 13.

    Lassey, K. R., Lowe, D. C. & Smith, A. M. The atmospheric cycling of radiomethane and the “fossil fraction” of the methane source. Atmos. Chem. Phys. 7, 2141–2149 (2007).

    CAS  Article  ADS  Google Scholar 

  14. 14.

    Etiope, G., Milkov, A. V. & Derbyshire, E. Did geologic emissions of methane play any role in Quaternary climate change? Global Planet. Change 61, 79–88 (2008).

    Article  ADS  Google Scholar 

  15. 15.

    Petrenko, V. V. et al. Measurements of 14C in ancient ice from Taylor Glacier, Antarctica constrain in situ cosmogenic 14CH4 and 14CO production rates. Geochim. Cosmochim. Ac. 177, 62–77 (2016).

    CAS  Article  ADS  Google Scholar 

  16. 16.

    Petrenko, V. V. et al. 14CH4 measurements in Greenland Ice: investigating last glacial termination CH4 sources. Science 324, 506–508 (2009).

    CAS  Article  ADS  Google Scholar 

  17. 17.

    Severinghaus, J. P. et al. Deep air convection in the firn at a zero-accumulation site, central Antarctica. Earth Planet. Sci. Lett. 293, 359–367 (2010).

    CAS  Article  ADS  Google Scholar 

  18. 18.

    Buizert, C. et al. Gas transport in firn: multiple-tracer characterisation and model intercomparison for NEEM, Northern Greenland. Atmos. Chem. Phys. 12, 4259–4277 (2012).

    CAS  Article  ADS  Google Scholar 

  19. 19.

    Rommelaere, V., Arnaud, L. & Barnola, J.-M. Reconstructing recent atmospheric trace gas concentrations from polar firn and bubbly ice data by inverse methods. J. Geophys. Res. Atmos. 102, 30069–30083 (1997).

    CAS  Article  ADS  Google Scholar 

  20. 20.

    Trudinger, C. et al. Reconstructing atmospheric histories from measurements of air composition in firn. J. Geophys. Res. Atmos. 107, (2002).

  21. 21.

    Smil, V. Energy Transitions: Global and National Perspectives (ABC-CLIO, 2016).

  22. 22.

    Hua, Q., Barbetti, M. & Rakowski, A. Z. Atmospheric radiocarbon for the period 1950–2010. Radiocarbon 55, 2059–2072 (2013).

    CAS  Article  Google Scholar 

  23. 23.

    Etiope, G. & Klusman, R. W. Microseepage in drylands: flux and implications in the global atmospheric source/sink budget of methane. Global Planet. Change 72, 265–274 (2010).

    Article  ADS  Google Scholar 

  24. 24.

    McGinnis, D. F., Greinert, J., Artemov, Y., Beaubien, S. & Wüest, A. Fate of rising methane bubbles in stratified waters: how much methane reaches the atmosphere? J. Geophys. Res. Oceans 111, C09007 (2006).

    Article  ADS  Google Scholar 

  25. 25.

    Leonte, M. et al. Rapid rates of aerobic methane oxidation at the feather edge of gas hydrate stability in the waters of Hudson Canyon, US Atlantic Margin. Geochim. Cosmochim. Acta 204, 375–387 (2017).

    CAS  Article  ADS  Google Scholar 

  26. 26.

    Sparrow, K. J. et al. Limited contribution of ancient methane to surface waters of the U.S. Beaufort Sea shelf. Sci. Adv. 4, eaao4842 (2018).

    Article  ADS  Google Scholar 

  27. 27.

    Nicewonger, M. R., Verhulst, K. R., Aydin, M. & Saltzman, E. S. 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 (2016).

    Article  ADS  Google Scholar 

  28. 28.

    Alvarez, R. A. et al. Assessment of methane emissions from the U.S. oil and gas supply chain. Science 361, 186–188 (2018).

    CAS  PubMed  PubMed Central  ADS  Google Scholar 

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This work was supported by US NSF awards OPP-1203779 (V.V.P.) OPP-1203686, OPP-0230452, ANT-0839031 (J.P.S.) ARC-1204084, ARC-1702920 (C.B.), a Packard Fellowship for Science and Engineering (V.V.P.), the National Institute of Water and Atmospheric Research through the Greenhouse Gases, Emissions and Carbon Cycle Science Programme (T.B.) and the Australian Government for the Centre for Accelerator Science at ANSTO through the National Collaborative Research Infrastructure Strategy (A.M.S.). We thank J. McConnell and P. Vallelonga for the interpretation of the ice core CFA data; P. Neff and E. Steig for sharing the ice-thinning model code; L. Davidge, J. Edwards, M. Pacicco and A. Adolph for assistance with firn air and ice core sampling; M. Jayred, L. Albershardt, T. Kuhl, D. Kirkpatrick and the US Ice Drilling programme for ice-drilling support; K. Gorham, J. Jenkins, D. Einerson, Polar Field Services and the 109th New York Air National Guard for logistical support; the Australian Antarctic Science Program for supporting the Law Dome drilling and firn air sampling and CSIRO GASLAB, in particular R. Langenfelds, for analysis of the firn air sample trace gas concentrations.

Author information




B.H. and V.V.P. designed the study and conducted field logistical and scientific preparations; B.H., V.V.P., M.N.D., C.B., P.F.P., R.B., J.S. and X.F. collected samples at Summit; B.H. measured [CO] and extracted CH4 and CO from firn air and ice core samples; C.B. developed the firn modelling code; B.H. and M.N.D. developed the box-model calculations; Q.H. and B.Y. graphitized the 14C samples; A.M.S. measured 14C; P.F.P. and I.V. measured δ13CO; S.E.M. measured δ13CH4; C.H. measured [CH4] and halogenated trace gases under the supervision of R.F.W.; E.D. supervised the firn air trace gas measurements; J.P.S. measured δXe/Kr, δKr/N2, δXe/N2 and δNe/N2 and collected Megadunes firn air samples; R.B. measured the δ15N of N2, the δ18O of O2, δO2/N2 and δAr/N2; D.E. collected and supervised the analyses of the Law Dome firn air samples; T.B. extracted CH4 from Megadunes and Law Dome samples; B.H. and V.V.P. analysed the data and B.H. drafted the manuscript with contribution from all authors.

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Correspondence to Benjamin Hmiel.

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The authors declare no competing interests.

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Supplementary information

Supplementary Information

This file contains details regarding ice core and firn air sample collection and analyses, procedural and in situ cosmogenic corrections for 14CH4, forward and inverse modeling of firn air and ice core data, atmospheric box modeling of 14CH4 and 13CH4. It also contains 5 Supplementary Figures and 8 Supplementary Tables.

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Hmiel, B., Petrenko, V.V., Dyonisius, M.N. et al. Preindustrial 14CH4 indicates greater anthropogenic fossil CH4 emissions. Nature 578, 409–412 (2020).

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