Better prediction of the effects of a rise in CO₂

These results demonstrate that natural changes in the CO₂ level have been large enough to contribute to natural climate changes during the last millennium. This is contrary to an assumption made by the Intergovernmental Panel on Climate Change (IPCC). The IPCC assumes that the effects of natural CO₂ changes on climate change over the last 1000 years have been negligible. A better understanding of natural CO₂ variations will enable improved prediction of the effects of the current increase in atmospheric CO₂ on the climate.

CO₂ is used by plants as a building material. Plants adapt the number of openings on the leaf surface (skin pores) to the amount of CO₂ in the air. When more CO₂ is present, the plant needs fewer skin pores to absorb CO₂. Consequently, the number of skin pores on fossil leaves can be used to reconstruct the amount of CO₂ in the past.

The results of this study are published this week in PNAS Early Edition:
Thomas B. van Hoof, Friederike Wagner-Cremer, Wolfram M. Kürschner, and Henk Visscher (2008)
A role for atmospheric CO₂ in preindustrial climate forcing

Press release 2008-41