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Atmospheric carbon dioxide concentrations over the past 60 million years

Pearson, Paul Nicholas and Palmer, Martin R. 2000. Atmospheric carbon dioxide concentrations over the past 60 million years. Nature 406 (6797) , pp. 695-699. 10.1038/35021000

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Abstract

Knowledge of the evolution of atmospheric carbon dioxide concentrations throughout the Earth's history is important for a reconstruction of the links between climate and radiative forcing of the Earth's surface temperatures. Although atmospheric carbon dioxide concentrations in the early Cenozoic era (about 60Myr ago) are widely believed to have been higher than at present, there is disagreement regarding the exact carbon dioxide levels, the timing of the decline and the mechanisms that are most important for the control of CO2 concentrations over geological timescales. Here we use the boron-isotope ratios of ancient planktonic foraminifer shells to estimate the pH of surface-layer sea water throughout the past 60 million years, which can be used to reconstruct atmospheric CO2 concentrations. We estimate CO2 concentrations of more than 2,000 p.p.m. for the late Palaeocene and earliest Eocene periods (from about 60 to 52 Myr ago), and ®nd an erratic decline between 55 and 40 Myr ago that may have been caused by reduced CO2 outgassing from ocean ridges, volcanoes and metamorphic belts and increased carbon burial. Since the early Miocene (about 24Myr ago), atmospheric CO2 concentrations appear to have remained below 500 p.p.m. and were more stable than before, although transient intervals of CO2 reduction may have occurred during periods of rapid cooling approximately 15 and 3 Myr ago.

Item Type: Article
Status: Published
Schools: Earth and Ocean Sciences
Subjects: Q Science > QC Physics
Publisher: Macmillan
ISSN: 0028-0836
Last Modified: 04 Jun 2017 03:00
URI: http://orca-mwe.cf.ac.uk/id/eprint/15261

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