CLIMATOLOGY

Modeling CO2's Ups and Downs

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Science  06 Jul 2001:
Vol. 293, Issue 5527, pp. 15
DOI: 10.1126/science.293.5527.15d

The atmospheric concentration of CO2 has risen and fallen in a remarkably regular manner during the past 400,000 years, in parallel with the waning and waxing of continental ice sheets driven by glacial cycles. Biological, chemical, and physical processes each have contributed to this variability, but modeling how much impact each of these processes has had remains a challenge.

One problem with most models is that they need to have their physical boundary conditions specified externally, which leaves unexplained the physical mechanisms that produced them. Gildor and Tziperman present a global meridional box model using a qualitative physical treatment of sea ice cover changes and vertical ocean mixing that does not need the physical state of the ocean to be prescribed. This enabled them to generate a CO2 record with a magnitude of variability consistent with observations. Their model explains the continuous evolution between glacial and interglacial states, rather than treating them as two different steady states, and reveals how ocean biogeochemistry can amplify glacial-interglacial climate variability. — HJS

Geophys. Res. Lett. 28, 2421 (2001).

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