HR: 14:05h
AN: PP22B-03 INVITED     [PDF]
TI: CO$_{2}$ as a Primary Driver of Phanerozoic Climate Change
AU: * Royer, D L
EM: droyer@psu.edu
AF: Pennsylvania State Univ., Dept. of Geosciences, University Park, PA 16801 United States
AU: Berner, R A
EM: robert.berner@yale.edu
AF: Yale Univ., Dept. of Geology and Geophysics, New Haven, CT 06520 United States
AB: Recent studies have purported to show a closer correspondence between Phanerozoic records of cosmic ray flux and temperature than between CO$_{2}$ and temperature. The role of the greenhouse gas CO$_{2}$ in controlling global temperatures has therefore been questioned. Here we review the geologic records of CO$_{2}$ and glaciations and find that CO$_{2}$ was low during periods of long-lived and widespread continental glaciations and moderately-high to high during other, warmer periods. The CO$_{2}$ record is likely robust because independent proxy records are highly correlated with CO$_{2}$ predictions from geochemical models. The Phanerozoic shallow water $\delta^{18}$O temperature record has been used to quantitatively test the importance of potential climate forcings, but it fails several first-order tests relative to well-established paleoclimatic indicators: both the early Paleozoic and Mesozoic are calculated to be too cold for too long. We explore the possible influence of seawater pH on the $\delta^{18}$O record and find that a pH-corrected record matches both the glacial and CO$_{2}$ records much better. Periodic fluctuations in the cosmic ray flux may be of some climatic significance, but are likely of second-order importance on a multi-million year timescale.
DE: 0325 Evolution of the atmosphere
DE: 0330 Geochemical cycles
DE: 1610 Atmosphere (0315, 0325)
SC: Paleoceanography and Paleoclimatology [PP]
MN: 2003 Fall Meeting