Tunable Diode Laser Spectroscopy for the Reconstruction of Atmospheric CO2-Concentrations of the Past 50,000 Years
The continuous measurements performed since 1958 at Mauna Loa (Hawaii) show that the global atmospheric CO2-concentration is increasing1. Since carbon dioxide is known to be an active greenhouse gas it is to be expected that global climate changes will result. Improved numerical climate models will eventually be able to predict the size and regional pattern of these changes. In order to validate such models it is important to know the history of the climate on Earth. Atmospheric air, which is enclosed in bubbles in polar ice samples offers a unique possibility to reconstruct the composition of the Earth’s atmosphere and in particular to determine how the CO2-content has varied in the past. Several deep drilling projects in Greenland and in Antarctica have ice cores made available that represent snow fall and corresponding trace substances from the atmosphere that reach up to 100,000 years and more back in time. Since these samples are obviously not easy to get it is important to use analytical techniques that needs as little of the valuable ice as possible for a measurement. For more than ten years now we have used the laser spectrometer2,3 described in the following sections, and with its use we were able to reconstruct the atmospheric CO2 content during the past 50,000 years4−7.
KeywordsMode Filter Trace Substance Absorption Line Width Numerical Climate Model Closed Cycle Refrigerator
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- 1.C. D. Keeling, R. B. Bacastov and T. P. Whorf, Measurement of the concentration of Carbon Dioxide at Mauna Loa Observatory, Haway, in W. C. Clark (ed.), “Carbon Dioxide Review”, Oxford University Press, New York, p. 377:385 (1982)Google Scholar
- 7.H. Oeschger and U. Siegenthaler, “How has the atmosperic concentration of CO2 changed”, in; “The Changing Atmosphere”, F. S. Rowland and I. S. A. Isaksen, eds., p. 5–23, John Wiley and Sons Ltd. (1988)Google Scholar