Leaves reveal higher past carbon dioxide variability

[Karl]

Environmental Research Web - October 08, 2008

While Antarctic ice cores indicate that atmospheric carbon-dioxide concentrations shifted by a maximum of 12 parts per million (ppm) by volume in pre-industrial times, a recent study of stomata in ancient leaves indicates the variability could have been much higher, at up to 34 ppm.

“We [have] proved that carbon dioxide did play an important role in climate variability during the pre-industrial part of the past 1000 years,” Tom van Hoof of the Netherlands Organisation of Applied Scientific Research told environmentalresearchweb. “Furthermore, the level of natural carbon-dioxide variation detected is comparable to about 30% of the man-induced carbon-dioxide increase of the past ˜150 years. The flexibility of the short-term carbon cycle is therefore bigger then previously assumed.”

The IPCC fourth assessment report assumed that carbon dioxide did not have a significant role as a climate-forcing factor before industry caused atmospheric levels of the gas to rise.

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