At the fourth international conference on carbon dioxide, held at Carqueiranne, France, 13-17 September, Charles Keeling, the scientist who orginated monitoring of atmospheric carbon dioxide concentrations, reveals that the gas last year increased at a slower-than-normal rate. 1992 was in fact the the largest negative anomaly record from the Mauna Loa (Hawaii) monitoring station in 35 years of data. Reductions in fossil fuel burning are clearly not the reason, Keeling says. (J.Grace, Terrestrial Initiative in Global Environmental Research, "An anomalous year for carbon dioxide," Tiger Eye, no 7, p.5-6, Autumn 1993).
NOTES: So where did the carbon go? It seems that the Pinatubo eruption may well have played a role. Important clues come from carbon isotopes in the gas. Photosynthesis takes up the the lighter isotope preferentially, and so tends to force the ratio of the heavier-to-lighter isotope up. Ocean uptake, however, has an insignificant effect on the ratio. The fact that the 13C/12C ratio does not show any anomaly, therefore, indicates that the ocean was responsible for the additional uptake of carbon dioxide.
One possible explanation is that the fall out from the eruption of Mount Pinatubo in 1991 caused a rapid fertilization of the oceans, leading a bloom in phytoplankton. Pinatubo erupted material containing some 500 million tons of iron, whereas fixation by phytoplankton of the 4 billion tonnes of carbon estimated to have been "withdrawn" from the atmosphere between the May 1991 and the end of 1992 would require only a fraction of a million tonnes.
(J.Grace, Terrestrial Initiative in Global Environmental Research, "An anomalous year for carbon dioxide," Tiger Eye, no 7, p.5-6, Autumn 1993).
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