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Celestial driver of Phanerozoic climate?
GSA Today

July 2003

By Dr. Shaviv and Dr. Veiser



Atmospheric levels of CO2 are commonly
assumed to be a main driver of
global climate. Independent empirical evidence
suggests that the galactic cosmic
ray flux (CRF) is linked to climate variability.
Both drivers are presently discussed
in the context of daily to millennial variations,
although they should also operate
over geological time scales. Here we analyze
the reconstructed seawater paleotemperature
record for the Phanerozoic (past
545 m.y.), and compare it with the variable
CRF reaching Earth and with the
reconstructed partial pressure of atmospheric
CO2 (pCO2). We find that at least
66% of the variance in the paleotemperature
trend could be attributed to CRF variations
likely due to solar system passages
through the spiral arms of the galaxy.
Assuming that the entire residual variance
in temperature is due solely to the CO2
greenhouse effect, we propose a tentative
upper limit to the long-term “equilibrium”
warming effect of CO2, one which is potentially
lower than that based on general
circulation models.

It is our attitude toward free thought and free expression that will determine our fate. There must be no limit on the range of temperate discussion, no limits on thought. No subject must be taboo. No censor must preside at our assemblies.

–William O. Douglas, U.S. Supreme Court Justice, 1952

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