, Volume 4, Issue 3, pp 221-237

The Montsouris series of carbon dioxide concentration measurements, 1877–1910

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The longest continuous record of measurements of atmospheric CO2 concentration available to date, that was made between 1877 and 1910 at the Montsouris Observatory in the outskirts of Paris, is presented and the methods used and the site are described. Annual, seasonal and daily variations in the record were considerable, especially between 1877 and 1880 and possible reasons for this high variability are discussed. Although no direct proof of the reliability of the series is available an attempt has been made to estimate this by comparisons with contemporary series whose precision is better known and also through an analysis of the results from the point of view of the major sources of error. The results suggest a precision of measurement better than 2%; analysis of the daily and the mean seasonal variation shows no evidence of any significant urban contamination of the Montsouris record. Mean decadal values of the Montsouris series show a marked rise in concentration from 283 ppm in the first decade to 313 ppm in the second, with a small and nonsignificant drop to 309 ppm in the third decade of the series. The results of the measurements are thus compatible with the hypothesis that a major and variable non-fossil fuel source of atmospheric CO2 was active during the last quarter of the nineteenth century.

Contribution from the Agricultural Research Organization, The Volcani Center, Bet Dagan, Israel. No. 254-E, 1981 series.