Modern Records of Atmospheric Methane (CH₄) and a 2000-year Ice-core Record from Law Dome, Antarctica

Introduction

This page provides an introduction and links to records of atmospheric methane (CH₄) over the last 2000 years, emphasizing large data bases each representing currently active stations. Records in recent decades (time period depending on location) have been obtained from samples of ambient-air at remote locations, which represent global atmospheric conditions rather than influences of local sources. The longer (2000-year) record is from the Law Dome ice core in Antarctica. The ice-core record has been merged with modern annual data from Cape Grim, Tasmania to provide a 2000-year record. A spline function has been fit to the data to provide a continuous time series of annual values. Longer-term records from Antarctic ice cores, back to 800,000 years before present, are available at http://cdiac.ornl.gov//trends/atm_meth/ice_core_methane.html.

These data have graciously been made freely available for access and distribution; the original investigators made the effort to obtain the data and assure their quality. Ice-core data are maintained by the World Data Center for Paleoclimatology, National Oceanic and Atmospheric Administration. To assure proper credit is given, please follow the instructions in the headers of the data files, in readme files, and/or at the end of this page when using any of this material. If data accessed from this site are to be used in a publication we strongly recommend some contact with the principal investigators at an early stage of the work to be sure the data are being interpreted and used correctly (NOAA insists on this; see instructions at the top of the header files). Neither the principal investigators nor CDIAC is responsible for misuse of these data.

Contributors

The following organizations have current data from multiple sites.

The Advanced Global Atmospheric Gases Experiment (AGAGE) and its European counterpart, the System for Observation of halogenated Greenhouse gases in Europe (SOGE).
The Commonwealth Scientific and Industrial Research Organization (CSIRO) of Australia, particularly David Etheridge who suggested the Law Dome data be included, and who provided it.
The Global Monitoring Division, Earth System Research Laboratory, National Oceanic and Atmospheric Administration (NOAA).
CDIAC maintains records for additional individual locations covering limited time periods.

Period of Record

13 C.E. - current

Station Locations

For locations of modern CH₄ sampling stations for AGAGE/SOGE and CSIRO: http://cdiac.ornl.gov/images/maps_m-ch4-n2o.jpg. For NOAA locations: http://www.esrl.noaa.gov/gmd/dv/iadv/ and click on a location to see which gases are measured there.

A map of Antarctic stations is given below, along with a detailed map of the Law Dome area.

Maps of Antarctica showing locations of the stations listed below; elevations are given in meters above sea level (masl). Law Dome (66°44'S, 112°50'E, 1390 masl), Dome C (75°06'S, 123°24'E, 3233 masl), Taylor Dome 77°48'S, 158°43'E, 2365 masl), Vostok (78°28'S, 106°52'E, 3500 masl), Dome A, (80°22'S, 77°22'°E, 4084 masl), the South Pole station (90°S, 2810 masl), and Siple Station (75°55'S, 83°55'W, 1054 masl.) The detailed map on the right is adapted from Etheridge et al. (1996), adapted, in turn, from Hamley et al. (1986).

Graphics

AGAGE: http://agage.eas.gatech.edu/images/Data_figures/gcmd_month/ch4_monS5.pdf
CSIRO: http://www.cmar.csiro.au/research/capegrim_graphs.html. For more detailed CO₂ graphics at Cape Grim, Tasmania, go to http://www.csiro.au/greenhouse-gases/. Immediately below the graph on the left hand side you will find a selection bar, select "methane".
NOAA: http://www.esrl.noaa.gov/gmd/dv/iadv/. This link gets to the visualization page for all gases. Move mouse over any point on the map to get the 3-letter station code (e.g. SPO is the South Pole).
CDIAC: 50-year moving averages of spline-function values of CH₄, CO₂, N₂O, are shown at http://cdiac.ornl.gov/images/three_gases_historical.jpg.

Data

AGAGE: http://cdiac.ornl.gov/ndps/alegage.html.
CSIRO: CSIRO_gaslab_data_Aug2011.zip.
NOAA: http://www.esrl.noaa.gov/gmd/dv/data/. Select methane from the second column. Information about station codes is at http://www.esrl.noaa.gov/gmd/dv/site/site_table2.html.
LAW DOME: A complete set of all Law Dome records, including the 2000-year time series of ice-core data merged with the modern cape-grim record, is available at: http://www.ncdc.noaa.gov/paleo/icecore/antarctica/law/law_data.html.
An earlier record from Law Dome is also archived at the CDIAC site. http://cdiac.ornl.gov/trends/atm_meth/lawdome_meth.html.
Data and graphics for individual locations covering limited time periods in recent decades are also available at CDIAC sites:
- Carbon-13 Isotopic Abundance and Concentration of Atmospheric Methane for Background Air in the Southern and Northern Hemispheres from 1978 to 1989 http://cdiac.ornl.gov/ndps/ndp049.html.
- Measurements of Atmospheric Methane and ¹³C/¹²C of Atmospheric Methane from Flask Air Samples (1999) http://cdiac.ornl.gov/ndps/quay.html.
- Atmospheric Methane at Cape Meares, Oregon, U.S.A.: A High-Resolution Data Base for the Period 1979-1992 http://cdiac.ornl.gov/ndps/db1007.html.
- Methane, Nonmethane Hydrocarbons, Alkyl Nitrates, and Chlorinated Carbon Compounds including 3 Chlorofluorocarbons (CFC-11, CFC-12, and CFC-113) in Whole-air Samples http://cdiac.ornl.gov/trends/otheratg/blake/blake.html.
- Mixing Ratios of CO, CO₂, CH₄, and Isotope Ratios of Associated ¹³C, ¹⁸O, and ²H in Air Samples from Niwot Ridge, Colorado, and Montaña de Oro, California, USA (January 2004) http://cdiac.ornl.gov/epubs/db/db1022/db1022.html.

Methods

Modern Data

Samples are analyzed using gas chromatography followed by flame ionization to produce ions in quantities which produce a measureable electronic signal. More detail on sampling, preparation, and measurement by NOAA is given for CH₄ in Dlugokencky et al. (2005). AGAGE data were obtained in a generally similar fashion; details on the AGAGE air sampling, preparation, and measurement process are found in Prinn et al. (2000), and on this web page. Information about the CSIRO sampling program is given in Francey (2003). Current information on reference scales and other details of measurement may be found at the following links:

AGAGE: http://agage.eas.gatech.edu/data_archive/agage/gc-md/readme.scale
CSIRO: See the pdf readme file for CH₄ at CSIRO_gaslab_data_Aug2011.zip
NOAA: In-situ data ftp://ftp.cmdl.noaa.gov/ccg/ch4/in-situ/README_surface_insitu_ch4.html.
Flask data ftp://ftp.cmdl.noaa.gov/ccg/ch4/flask/README_surface_flask_ch4.html.

Law Dome Ice Core Data

Air was extracted from the ice core samples using a dry extraction "cheese grater" and cryogenic trapping technique developed by Etheridge et al. (1996) with only minor alterations (MacFarling Meure, 2004). The trapped air samples were analyzed by gas chromatography and the trace gas concentrations are reported on the calibration scales maintained by CSIRO GASLAB (Francey et al., 2003).

The ice cores were dated by counting the annual layers of oxygen isotope ratio (δ¹⁸O in H₂O), of ice electroconductivity measurements (ECM) and of hydrogen peroxide (H₂O₂). For these three parameters, each core displayed clear, well-preserved seasonal cycles allowing a dating accuracy of about 5 years, and exact dating in recent centuries where material from known volcanoes is present (ftp://ftp.ncdc.noaa.gov/pub/data/paleo/icecore/antarctica/law/law2006.txt). The Law Dome data were merged with modern deseasonalised flask and in situ records for CH₄ at Cape Grim, Tasmania, and a spline function was fit to the result to provide a continuous time series of annual values extending back approximately 2000 years before the present.

For more details about methodology see: http://cdiac.ornl.gov/trends/co2/law_dome_methods.html.

Trends

Atmospheric methane began its modern upswing around 1800, 50-100 years before carbon dioxide or nitrous oxide did. (see this figure) This is possibly due to an expanding agriculture. Focusing on the last few decades, atmospheric methane was steadily increasing before leveling off temporarily during the first few years of the 21^st Century. It began to increase again around 2007. (see this graph)

Northern Hemisphere amounts change before those in the Southern Hemisphere, suggesting the Northern Hemisphere is the net source of the overall increase. However, locations of sources and sinks and the nature of the processes involved, preclude any simple explanations. Natural sources of methane include wetlands and microorganisms in the digestive systems of animals. Recent methane increases also arise from mining, fossil-fuel extraction and processing, and from landfills as well as from expansion and intensification of agriculture. The major atmospheric sink is removal by the hydroxyl radical.

References

References to Ice-Core Data

The Law Dome record consists of ice-core data, firn data, and atmospheric samples at Cape Grim Tasmania. Newer results which fill in gaps, double the length of record from approximately 1000 years to 2000 years, and include CH₄, were published and explained in detail in MacFarling Meure 2004 and MacFarling Meure et al. 2006. Some new CH₄ results were also published in Ferretti et al. 2005.

Etheridge, D.M., G.I. Pearman and F. de Silva. 1988. Atmospheric trace-gas variations as revealed by air trapped in an ice core from Law Dome, Antarctica. Ann. Glaciol. 10, 28-33.
Etheridge, D.M., L.P. Steele, R.L. Langenfelds, R.J. Francey, J.-M. Barnola and V.I. Morgan. 1996. Natural and anthropogenic changes in atmospheric CO₂ over the last 1000 years from air in Antarctic ice and firn. Journal of Geophysical Research 101, 4115-4128.
Ferretti, D.F., J.B. Miller, J.W.C. White, D.M. Etheridge, K.R. Lassey, et al. 2005. Unexpected Changes to the Global Methane Budget over the Last 2,000 Years. Science 309 (5741): 1714-1717.
Hamley. T.C., V.I. Morgan, R.J. Thwaites, and X.Q Gao. 1986. An ice-core drilling site at Law Dome summit. Wilkes Land, Antarctica, Research Note 37, Australian Antarctic Research Expedition, Tasmania.
MacFarling Meure, C. 2004. The natural and anthropogenic variations of carbon dioxide, methane and nitrous oxide during the Holocene from ice core analysis. PhD thesis, University of Melbourne.
MacFarling Meure, C., D. Etheridge, C. Trudinger, P. Steele, R. Langenfelds, T. van Ommen, A. Smith and J. Elkins. 2006. The Law Dome CO₂, CH₄ and N₂O Ice Core Records Extended to 2000 years BP. Geophysical Research Letters 33, 14, L14810 10.1029/2006GL026152.
Morgan, V.I., C.W. Wookey, J. Li, T.D. van Ommen, W. Skinner and M.F. Fitzpatrick. 1997. Site information and initial results from deep ice drilling on Law Dome. J. Glaciol. 43, 3-10.
Trudinger, C.M., I.G. Enting, D.M. Etheridge, R.J. Francey, V.A. Levchenko, et al. 1997. Modeling air movement and bubble trapping in firn. Journal of Geophysical Research 102, (D6) 6747-6763.

References Specific to the Law Dome 2000-year Ice-Core Record

Francey, R. J., L.P. Steele, D.A. Spencer, R.L. Langenfelds, R.M. Law, et al. 2003. The CSIRO measurement of greenhouse gases in the global atmosphere, in Baseline Atmospheric Program (Australia), 1999–2000, edited by N. W. Tindale, N. Derek and P. J. Fraser, Bureau of Meteorology and CSIRO Atmospheric Research, Melbourne, Australia (pp. 42-53).
Langenfelds, R.L., P.J. Fraser, R.J. Francey, L.P. Steele, L.W. Porter and C.E. Allison. 1996. The Cape Grim air archive: The first seventeen years, 1978-1995, In: Baseline Atmospheric Program (Australia) 1994-1995. edited by Francey, R.J., A.L. Dick, and N. Derek, Bureau of Meteorology and CSIRO Division of Atmospheric Research, Melbourne, Australia. (pp. 53-70).
Langenfelds, R.L., L.P. Steele, M.V. Van der Schoot, L.N. Cooper, D.A. Spencer and P.B. Krummel. 2004. Atmospheric methane, carbon dioxide, hydrogen, carbon monoxide and nitrous oxide from Cape Grim flask air samples analysed by gas chromatography. In: Baseline Atmospheric Program Australia. 2001-2002, edited by J.M. Cainey, N. Derek, and P.B. Krummel. Melbourne: Bureau of Meteorology and CSIRO Atmospheric Research. (pp. 46-47).
Langenfelds, R.L., P.J. Fraser, L.P. Steele and L.W. Porter. 2004. Archiving of Cape Grim Air. In: Baseline Atmospheric Program Australia. 2001-2002, edited by J.M. Cainey, N. Derek and P.B. Krummel. Melbourne: Bureau of Meteorology and CSIRO Atmospheric Research. (p. 48).
Rigby, P.G., R.G. Prinn, R.G. Fraser, P.G. Simmonds, R.L. Langenfelds, et al. 2008. Renewed growth of atmospheric methane, Geophysical Research Letters 35, L22805, doi:10.1029/2008GL036037.

General References

Cunnold, D.M., L.P. Steele, P.J. Fraser, P.G. Simmonds, R.G. Prinn, R.F. Weiss, L.W. Porter, R.L. Langenfelds, H.J. Wang, L. Emmons, X.X. Tie, and E.J. Dlugokencky. 2002. in situ measurements of atmospheric methane at GAGE/AGAGE sites during 1985-2000 and resulting source inferences. J. Geophys. Res. 107 (D14), 4225. doi:10.1029/2001JD001226.
Dlugokencky, E.J., R.C. Myers, P.M. Lang, K.A. Masarie, A.M. Crotwell, et al. 2005. Conversion of NOAA atmospheric dry air CH₄ mole fractions to a gravimetrically prepared standard scale, Journal of Geophysical Research-Atmospheres 110(D18), 10.1029/2005JD006035.
Dlugokencky, E. J., L. Bruhwiler, J. W. C. White, L. K. Emmons, P. C. Novelli, et al. 2009. Observational constraints on recent increases in the atmospheric CH₄ burden, Geophysical Research Letters 36, L18803, doi:10.1029/2009GL039780.
Miller, B. R., R. F. Weiss, P. K. Salameh, T. Tanhua, B. R. Greally, J. Mühle, P. G. Simmonds. 2008. Medusa: A Sample Preconcentration and GC/MS Detector System for in situ Measurements of Atmospheric Trace Halocarbons, Hydrocarbons, and Sulfur Compounds, /Analytical Chemistry/., ASAP Article; doi: 10.1021/ac702084k.
Prinn, R.G., R.F. Weiss, P.J. Fraser, P.G. Simmonds, D.M. Cunnold, F.N. Alyea, S. O'Doherty, P. Salameh, B.R. Miller, J. Huang, R.H.J. Wang, D.E. Hartley, C. Harth, L.P. Steele, G. Sturrock, P.M. Midgley, and A. McCulloch. 2000. A History of Chemically and Radiatively Important Gases in Air deduced from ALE/GAGE/AGAGE, J. of Geophys. Res.-Atmospheres 105 (D14), 17,751-17,792.
Rigby, R. G., Prinn, P. J. Fraser, P. G. Simmonds, R. L. Langenfelds, J. Huang, D. M. Cunnold, L. P. Steele, P. B. Krummel, R. F. Weiss, S. O’Doherty, P. K. Salameh, H. J. Wang, C. M. Harth, J. Mühle, and L. W. Porter. 2008. Renewed growth of atmospheric methane, Geophys. Res. Lett. 35, L22805. doi:10.1029/2008GL036037.

Citing This Material

AGAGE: The general reference for AGAGE data is: Prinn et al. 2000; for CH₄ , see also Cunnold et al., 2002, and Rigby et al. 2008. These references are given above.

CSIRO: CSIRO requests that use of these data in any paper or presentation be accompanied by acknowledgement of the source of the data (CSIRO Marine and Atmospheric Research GASLAB) and that the version of the data (as specified by release date) be explicitly stated. For additional references to cite, please consult the readme file (pdf or doc) for CH₄ in the list of files found at CSIRO_gaslab_data_Aug2011.zip.

NOAA: Citations for NOAA data are given "readme" files for each species. ftp://ftp.cmdl.noaa.gov/ccg.

LAW DOME ICE CORE DATA For data including the Law dome ice-core records alone or merged with the Cape Grim data, cite:

Etheridge, D.M., et al. 2010. Law Dome Ice Core 2000-Year CO₂, CH₄, and N₂O Data. IGBP PAGES/World Data Center for Paleoclimatology Data Contribution Series # 2010-070. NOAA/NCDC Paleoclimatology Program, Boulder CO, USA.

We recommend also citing: MacFarling-Meure, et al. 2006 and, Etheridge 1996 from the references above in any published work.

If accessing the data from this site: please also cite: Carbon Dioxide Information Analysis Center, Oak Ridge National Laboratory, U.S. Department of Energy.

If citing material from this page only, cite as: Modern Records of Atmospheric Methane (CH₄) and a 2000-year Ice-core Record from Law Dome Ice Cores in Antarctica, Carbon Dioxide Information Analysis Center, Oak Ridge National Laboratory. http://cdiac.ornl.gov/trends/atm_meth/modern_methane.html

Modern Records of Atmospheric Methane (CH4) and a 2000-year Ice-core Record from Law Dome, Antarctica