17 May 2001

Atmospheric CO₂: Leafing through 300 Myr

Plant samples from old herbariums show that as atmospheric CO₂ levels have risen during the past 200 years of industrial fossil fuel consumption, plants have responded by increasing the density of the stomata on their leaves. So if plants have always behaved in this way, the fossil record should contain a history of CO₂ levels down the ages. A continuous 300-million-year record of stomatal abundance in the fossils of plants related to today's ginkgo, or maidenhair tree, proves this supposition true, providing perhaps the longest and most detailed 'palaeobarometer' of atmospheric CO₂ so far constructed. The variations revealed are consistent with several brief phases of 'greenhouse' warming and 'icehouse' cooling, known from climate proxies, which extends back in time our understanding of the link between CO₂ and climate.

A 300-million-year record of atmospheric carbon dioxide from fossil plant cuticles
GREGORY J. RETALLACK
Nature 411, 287-290 (17 May 2001)
| First Paragraph | Full Text | PDF (173 K) | Supplementary Information |

Leaf sensor for CO₂ in deep time
WOLFRAM M. K�RSCHNER
How long have CO₂ and climate been linked? At least 300 million years, according to the results of a neat technique that exploits the relationship between concentrations of CO₂ in the atmosphere and pores in leaves.
Nature 411, 247-248 (17 May 2001)
| Full Text | PDF (216 K) |

17 May 2001 table of contents