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 Nitrous Oxide (N2O) and a 2000-year Ice-core Record from Law Dome, Antarctica


This page provides an introduction and links to records of atmospheric nitrous oxide (N2O) 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 changing 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 time series of annual values ending with the most recent data. A spline function 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 on the CDIAC 800,000 Year Ice-Core Records of Atmospheric Nitrous Oxide (N2O) page.

The World Data Center for Greenhouse Gases 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 may be useful for investigating influences of large urban or agricultural areas on N2O 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 Advanced Global Atmospheric Gases Experiment (AGAGE) and its European Counterpart, the System for Observation of halogenated Greenhouse gases in Europe (SOGE).
  2. 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.
  3. The Global Monitoring Division, Earth System Research Laboratory, National Oceanic and Atmospheric Administration (NOAA) and
  4. The World Data Center for Paleoclimatology at the National Oceanic and Atmospheric Administration (NOAA), which archives the ice-core data.
  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


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:


Modern Record

Samples are analyzed using gas chromatography followed electron capture in which available electrons are selectively captured in proportion to the amount of substance being analyzed, thereby creating an electrical signal which can be measured. More detail on sampling, preparation, and measurement by NOAA is given by Hall et al. (2007) and for CSIRO in the readme file for N2O available from the data link given above. 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 at 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:

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 (d18O 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. ( 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:


Nitrous oxide began to increase from a preindustrial value of around 260-270 parts per billion (ppb) during the first part of the 20th Century. (see this figure) A steady increase from about 300 ppb to 325 ppb occurred from 1980 to 2010. (see this graph)

Northern Hemisphere amounts are slightly greater than in the Southern Hemisphere, suggesting the Northern Hemisphere is the net source of the overall increase. Increased use of nitrogen fertilizers and subsequent decomposition by denitrifying bacteria is believed to contribute most to the recent increases in N2O (IPCC 2013). Nitrous oxide also arises from fossil-fuel combustion and nitric acid production.


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, have doubled the length of record from approximately 1000 years to 2000 years, and now include N2O, were published and explained in detail in MacFarling Meure 2004 and MacFarling Meure et al. 2006.

  • 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.
  • 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 to the Cape Grim (Modern Instrumental) 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).

General References

  • Hall, B. D., G. S. Dutton and J. W. Elkins. 2007. The NOAA nitrous oxide standard scale for atmospheric observations, Journal of Geophysical Research-Atmospheres 112, 10.1029/2006JD007954.
  • 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.
  • IPCC, 2013: Climate Change 2013: The Physical Science Basis. Contribution of Working Group I to the Fifth Assessment Report of the Intergovernmental Panel on Climate Change [Stocker, T. F., D. Qin, G.-K. Plattner, M. Tignor, S. K. Allen, J. Boschung, A. Nauels, Y. Xia, V. Bex and P. M. Midgley (eds.)]. Cambridge University Press, Cambridge, United Kingdom and New York, NY, USA

Citing This Material

Modern N2O Data

  • AGAGE: The general reference for AGAGE data is: Prinn et al. 2000; for N2O , see also Prinn et al. 1990. Both 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.
  • NOAA: Citations for NOAA/ESRL data are given in the beginning material in each data file (scroll down to Data Use Policy. For flask data see For in-situ data see:
  • 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 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 Nitrous Oxide (N2O) and a 2000-year Ice-core Record from Law Dome Ice Cores in Antarctica, Carbon Dioxide Information Analysis Center, Oak Ridge National Laboratory, U.S. Department of Energy.