NOTICE (March 2018): This website provides access to the CDIAC archive data temporarily. It will be gradually transitioned into data packages in the new ESS-DIVE archive. This site will continue to operate in parallel during and after the transition, and will be retired at a future date. If you have any questions regarding the data or the transition, please contact

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Modern Records of Atmospheric Carbon Dioxide (CO2) and a 2000-year Ice-core Record from Law Dome, Antarctica


This page provides an introduction and links to records of atmospheric carbon dioxide (CO2) concentrations over the last 2000 years, emphasizing large data bases each representing many currently active stations. Records since about 1960 (depending on location) have been obtained from samples of ambient-air at remote stations, which represent changing global atmospheric concentrations 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 ending with the most recent data. A spline has been fit to the data to provide a continuous time series of annual values. Longer-term series from Antarctic ice cores, back to 800,000 years before present, are available here.

The World Data Center for Greenhouse Gases (WDCGG) provides data for stations around the world. In addition to the remote stations that reflect global background conditions, many stations are located in areas influenced by large urban or regional sources. These records are useful for investigating influences of large populated areas on CO2 concentrations.

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 (Some organizations insist on this; see instructions on the home pages or at the top of the header files). Neither the principal investigators nor CDIAC is responsible for misuse of these data.


The following organizations have current data from multiple sites.

  1. 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
  2. The Global Monitoring Division, Earth System Research Laboratory, National Oceanic and Atmospheric Administration (NOAA)
  3. The World Data Center for Paleoclimatology at the National Oceanic and Atmospheric Administration (NOAA), which archives the ice-core data
  4. The Scripps Institution of Oceanography (Scripps CO2 program)
  5. The WDCGG archives modern data obtained from instruments at locations around the world. These data may not always be as up to date as those from the individual sources listed above, but this site provides greater geographical coverage.
  6. CDIAC maintains records for additional individual locations covering limited time periods.

Period of Record

0 C.E. - Current

Station Locations

  • For NOAA locations click on a location to see which gases are measured there.
  • For WDCGG locations select CO2 from the parameter list.
  • CDIAC: 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).

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Find Information about 3-letter station codes here.


Modern Record

We recommend the detailed and readable account of the air sampling, preparation, measurement process, and calibration scales given by NOAA. Additional material is given in Conway et al. (1994). Basically, infrared radiation of known intensity in CO2 absorbing wavelengths is transmitted through sampled air and the amount of radiation passing through to a detector is measured and converted to a voltage value on a scale which is carefully calibrated against reference gases of known CO2 concentration. Current information on reference scales and other details of measurement for CSIRO may be found at the following links:

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) concentrations. 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.

The Law Dome data were merged with modern deseasonalised flask and In Situ records for CO2. 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 this CDIAC page.


The merged, 2000-year record indicates that atmospheric CO2 levels have substantially increased beyond their preindustrial values which fluctuated around 280 parts per million (ppm) for most of the period, with a slight dip from around 1600 to 1800 C.E. The Intergovernmental Panel on Climate Change defined preindustrial concentrations as those prior to 1750. Atmospheric CO2 concentrations rose from around 277 ppm (IPCC, 2007) in 1750 to a global average of around 388 ppm in 2010 (386 ppm at Cape Grim and the South Pole; Southern Hemisphere concentrations tend to lag Northern Hemisphere values).


  • Conway, T.J., P.P. Tans, L.S. Waterman, K.W. Thoning, D.R. Kitzis, K.A. Masarie, and N. Zhang. 1994. Evidence for interannual variability of the carbon cycle from the NOAA/CMDL global air sampling network, Journal of Geophysical Research 99, 22831-22855.
  • IPCC, 2007: Climate Change 2007: The Physical Science Basis. Contribution of Working Group I to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change [Solomon, S., D. Qin, M. Manning, Z. Chen, M. Marquis, K.B. Averyt, M. Tignor and H.L. Miller (eds.)]. Cambridge University Press, Cambridge, United Kingdom and New York, NY, USA, 996 pp. (See p. 140).

References Specific to the Cape Grim (modern instrumental) Record

  • Francey, R. J., 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).

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

  • 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.
  • 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.
  • 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.

Citing this Material

Modern CO2 Data

  • 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.
  • NOAA: Citations to NOAA personnel are given in the "readme" files for each species.
  • SCRIPPS: Scripps requests citing one of the references listed on this page (scroll to the bottom of the page). We also suggest the reference given at the top of each data page, for example:
    R. F. Keeling, S. C. Piper, A. F. Bollenbacher and S. J. Walker, Scripps CO2 Program, Scripps Institution of Oceanography, University of California, La Jolla, California USA 92093-0244.
  • WDCGG: Citation instructions are given in red on the WDCGG home page. By use of these data "“you accept that an offer of co-authorship will be made through personal contact with the data providers or owners whenever substantial use is made of their data. In all cases, an acknowledgement must be made to the data providers or owners and the data centre when these data are used within a publication."

Law Dome Ice-Core Data

These records are maintained by the World Data Center for Paleoclimatology at the National Oceanic and Atmospheric Administration (NOAA). 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.


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 Carbon Dioxide (CO2) and a 2000-year Ice-core Record from Law Dome, Antarctica, Carbon Dioxide Information Analysis Center, Oak Ridge National Laboratory, U.S. Department of Energy. Path: