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Atmospheric Carbon Dioxide Record from American Samoa

graphics Graphics   data Data


R.F. Keeling, S.C. Piper, A.F. Bollenbacher and J.S. Walker
Scripps Institution of Oceanography,
University of California,
La Jolla, California 92093-0244, U.S.A.

Period of Record



At Cape Matatula, American Samoa, 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. In May 1983, the CO2-in-air 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 American Samoa (Cape Matatula), U.S. Territory

American Samoa (Cape Matatula), U.S. Territory,
Pacific Ocean rocky costal promontory
14°15' S, 170°34' W
30 m above MSL


NOAA established a monitoring project to observe the sea-level climate and atmospheric constituents of the tropical Southern Hemisphere at Cape Matatula, American Samoa, in 1973. NOAA operates both a continuous monitoring program (Waterman et al. 1989) and a flask sampling program (Conway et al. 1988) at Cape Matatula. Independently of NOAA, Scripps Institution of Oceanography (SIO) has also collected flask samples at American Samoa since 1981. On the basis of flask samples collected by SIO, the annual average of the fitted concentrations of CO2 rose from 340.58 ppmv in 1982 to 382.05 ppmv in 2007. This represents an average annual growth rate of 1.66 ppmv per year at American Samoa.


  • Conway, T.J., P. Tans, L.S. Waterman, K.W. Thoning, K.A. Masarie, and R.H. Gammon. 1988. Atmospheric carbon dioxide measurements in the remote global troposphere, 1981-1984. Tellus 40B:81-115.
  • Keeling, C.D., R.B. Bacastow, A.F. Carter, S.C. Piper, T.P. Whorf, M. Heimann, W.G. Mook, and H. Roeloffzen. 1989. A three-dimensional model of atmospheric CO2 transport based on observed winds: 1. Analysis of observational data. In D.H. Peterson (ed.), Aspects of Climate Variability in the Pacific and the Western Americas. Geophysical Monograph 55:165-235.
  • 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.
  • Waterman, L.S., D.W. Nelson, W.D. Komhyr, T.B. Harris, K.W. Thoning, and P.P. Tans. 1989. Atmospheric carbon dioxide measurements at Cape Matatula, American Samoa, 1976-87. Journal of Geophysical Research 94(D12):14817-29.

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.