Atmospheric Carbon Dioxide Record from American Samoa

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Investigators

C.D. Keeling and T.P. Whorf
Scripps Institution of Oceanography,
University of California,
La Jolla, California 92093-0244, U.S.A.

Period of Record

1981-2004

Methods

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).

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

Trends

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 concentration of CO₂ rose from 340.60 ppmv in 1982 to 375.94 ppmv in 2004. This represents an average annual growth rate of 1.6 ppmv per year at American Samoa.

References

• 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.
• 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.