Atmospheric CO₂ from Continuous Air Samples at Mauna Loa Observatory, Hawaii, U.S.A.

Graphics    Data

C.D. Keeling and T.P. Whorf

Carbon Dioxide Research Group, Scripps Institution of Oceanography, University of California, La Jolla, California 92093-0444, U.S.A.

Period of Record

March 1958 - December 2001

Methods

An Applied Physics Corporation (APC) nondispersive infrared gas analyzer was used to obtain atmospheric CO₂ concentrations, based on continuous data (four measurements per hour) from atop intake lines on several towers. Steady data periods of not less than six hours per day are required; if no such six-hour periods are available on any given day, then no data are used that day. Weekly averages were calculated for most weeks throughout the approximately 44 years of record. The continuous data for year 2000 is compared with flask data from the same site in the graphics section.

Mauna Loa, Hawaii, U.S.A. Barren lava field of an active volcano 19°32' N, 155°35' W, 3397 m above MSL

Trends

This is the longest continuous record of CO₂ in the world. The annual range of about 7 ppmv and the shape of the annual wave are well defined by these weekly data. An upward trend from about 315 ppmv in 1958 to about 370 ppmv in 2001 is evident; this amounts to an increase of about 1.3 ppmv/year (see the monthly averaged data ).

References

• Guenther, P.R., A. Bollenbacher, C.D. Keeling, and D. Moss. 2002 Technical Report: Infrared Analyses of NOAA Primary CO₂-in-Air Reference Gas Standards at SIO, 1991-1999.
• Guenther, P.R., G. Emanuele, and C.D. Keeling. 2002. Alternative Formulation of 1985-1999 Calibrations after Re-calibration of 4cc Chanber Volume of Mercury Manometer. Addendium to: Scripps Reference Gas Calibration System for Carbon-Dioxide-in Nitrogen and Carbon Dioxide-in-Air Standards: Revision of 1999, February 2002.
  See Diagram of the constant-volume mercury-column manometer.
• 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, 165-236, Geophysical Monograph 55, American Geophysical Union, Washington, DC.
• Keeling, C.D., T.P. Whorf, M. Wahlen & J. van der Plicht. 1995. Interannual extremes in the rate of rise of atmospheric carbon dioxide since 1980, Nature 375, 666-670.
• 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, 165-236, Geophysical Monograph 55, American Geophysical Union, Washington, DC.
• Keeling, C.D., S.C. Piper, R.B. Bacastow, M. Wahlen, T.P. Whorf, M. Heimann, and H.A. Meijer. 2001. Exchanges of Atmospheric CO₂ and ¹³CO₂ with the Terrestrial Biosphere and Oceans from 1978 to 2000. I. Global Aspects. SIO Reference No. 01-06 (Revised from SIO Reference No. 00-21), June 2001.
• 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 Appendix and Addendum). SIO Reference Series No. 01-11.
  See Diagram of the constant-volume mercury-column manometer.
• Pales, J. C., and C. D. Keeling. 1965. The concentration of atmospheric carbon dioxide in Hawaii, J. Geophys. Res. 70, 6053-6076.

10/2004