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Science 19 June 2009:
Vol. 324. no. 5934, pp. 1551 - 1554
DOI: 10.1126/science.1171477
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Reports

Atmospheric Carbon Dioxide Concentration Across the Mid-Pleistocene Transition

Bärbel Hönisch,1 N. Gary Hemming,1,2 David Archer,3 Mark Siddall,4 Jerry F. McManus1

The dominant period of Pleistocene glacial cycles changed during the mid-Pleistocene from 40,000 years to 100,000 years, for as yet unknown reasons. Here we present a 2.1-million-year record of sea surface partial pressure of CO2 (PCO2), based on boron isotopes in planktic foraminifer shells, which suggests that the atmospheric partial pressure of CO2 (pCO2) was relatively stable before the mid-Pleistocene climate transition. Glacial PCO2 was ~31 microatmospheres higher before the transition (more than 1 million years ago), but interglacial PCO2 was similar to that of late Pleistocene interglacial cycles (<450,000 years ago). These estimates are consistent with a close linkage between atmospheric CO2 concentration and global climate, but the lack of a gradual decrease in interglacial PCO2 does not support the suggestion that a long-term drawdown of atmospheric CO2 was the main cause of the climate transition.

1 Department of Earth and Environmental Sciences, Lamont-Doherty Earth Observatory of Columbia University, NY 10964–8000, USA.
2 School of Earth and Environmental Sciences, Queens College, New York, NY, 11367–1597, USA.
3 Department of Geophysical Sciences, University of Chicago, Chicago, IL 60637, USA.
4 Department of Earth Sciences, University of Bristol, Bristol, UK.

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Changes in Temperature, Ice, and CO2 During the Mid-Pleistocene Transition
Roderik S. W. van de Wal, et al.
Science Online, 18 Sep 2009 [Full text]

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