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Atmospheric Carbon Dioxide Record from Christmas Island, Kiribati

graphics Graphics   data Data


R.F. Keeling, S.C. Piper, A.F. Bollenbacher and J.S. Walker
Carbon Dioxide Research Group,
Scripps Institution of Oceanography,
University of California,
La Jolla, California 92093-0444, U.S.A.

Period of Record



At Christmas Island, weekly air samples are collected in 5-L evacuated glass flasks exposed in triplicate. Flasks are returned to the SIO for CO2 determinations, which are made using an Applied Physics Corporation nondispersive infrared gas analyzer. The 1972-1976 portion of this record is based on air samples collected at Fanning Island. The 1977-1983 portion of this record is based on air samples collected at both Christmas Island and Fanning Island. From 1983 to present the record is based solely on air samples collected at Christmas Island. In May 1983, the CO2-in-N2 calibration gases were replaced with CO2-in-air calibration gases, which are currently used (Keeling et al. 2002). Data are in terms of the Scripps "03A" calibration scale.

Map showing location of Christmas Island, Kiribati

Christmas Island, Kiribati
Pacific Ocean island seashore
2°00' N, 157°18' W
3 m above MSL


On the basis of flask samples collected at Christmas Island and analyzed by SIO, the annual average of the fitted concentrations of CO2 rose from 332.04 ppmv in 1975 to 383.61 ppmv in 2007. This represents an average annual growth rate of over 1.61 ppmv per year in the fitted values at Christmas Island.


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  • Bacastow, R.B., and C.D. Keeling. 1981. Atmospheric carbon dioxide concentration and the observed airborne fraction. In B. Bolin (ed.), Carbon Cycle Modelling, SCOPE 16. John Wiley and Sons, New York.
  • Bacastow, R.B., J.A. Adams, Jr., C.D. Keeling, D.J. Moss, T.P. Whorf, and C.S. Wong. 1980. Atmospheric carbon dioxide, the Southern Oscillation, and the weak 1975 El Niño. Science 210:66-68.
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  • Keeling, C.D., P.R. Guenther, G. Emanuele III, A. Bollenbacher, and D.J. Moss. 2002. Scripps Reference Gas Calibration System for Carbon Dioxide-in-Nitrogen and Carbon Dioxide-in-Air Standards: Revision of 1999 (with Addendum). SIO Reference Series No. 01-11.
  • Keeling, C.D., S.C. Piper, R.B. Bacastow, M. Wahlen, T.P. Whorf, M. Heimann, and H.A. Meijer, Atmospheric CO2 and 13CO2 exchange with the terrestrial biosphere and oceans from 1978 to 2000: Observations and carbon cycle implications, pages 83-113, in "A History of Atmospheric CO2 and its effects on Plants, Animals, and Ecosystems", editors, Ehleringer, J.R., T.E. Cerling, M.D. Dearing, Springer Verlag, New York, 2005.
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CITE AS: Keeling, R.F., S.C. Piper, A.F. Bollenbacher and J.S. Walker. 2008. Atmospheric CO2 records from sites in the SIO air sampling network. In Trends: A Compendium of Data on Global Change. Carbon Dioxide Information Analysis Center, Oak Ridge National Laboratory, U.S. Department of Energy, Oak Ridge, Tenn., U.S.A.