Climate Science

Rete Mirabile

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Science  18 Feb 2005:
Vol. 307, Issue 5712, pp. 1015
DOI: 10.1126/science.307.5712.1015a

The atmospheric concentration of CO2 and the climate are connected by an intricate web of positive and negative feedbacks. The CO2 content of the atmosphere is increased by volcanic and metamorphic degassing and decreased by the chemical weathering of silicate rocks; yet another important influence is the vascular land plants. A fundamental difficulty in understanding the role of plants, however, is that long-term changes in CO2 and climate affect terrestrial plant development and evolution, which in turn has consequences for the burial of organic matter in sediments and chemical weathering.

Beerling and Berner present a systems analysis of the physiological and geochemical processes linking plants and CO2 on geological time scales and pay special attention to how this wondrous network prevents runaway changes in CO2 and catastrophic planetary warming. By incorporating processes that affect CO2 on million-year time scales, such as evolution and weathering, and ones occurring on much shorter time scales, such as how terrestrial ecosystems regulate the land/ atmosphere exchange of water vapor and recycling of precipitation, they uncover important feedback loops not previously identified. They also find that the biota exerted a destabilizing influence on climate regulation in the Paleozoic, and this quickened the rates of terrestrial plant and animal evolution, which accelerated the diversification of terrestrial tetrapods and insects, and caused a large rise in the concentration of atmospheric oxygen. — HJS

Proc. Natl. Acad. Sci. U.S.A. 102, 1302 (2005).

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