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Figure 2.25. Corrected changes in tropical sea temperatures due to change in pH from
changing CO
2
concentration (adapted from Royer et al., 2004).
correction to
D
T that is an implicit function of R(CO
2
). It is then not surprising
that a correlation between
D
T and R(CO
2
) is obtained. This would be the case
irrespective of the R(CO
2
) model utilized. A proper analysis, which avoids this
bootstrapping and considers a more realistic pH correction, shows that the global
temperature sensitivity to CO
2
is still relatively small. In summary, while we
acknowledge that the proposition of Royer et al. (2004) has some merit and likely
will result in some modification of the
d
18
O signal, the cosmic ray flux still
remains the primary climate driver for any realistic pH correction. Even for
the scenario that entirely disregards the ice-volume effect, the impact of cosmic
ray flux would still be at par with that of CO
2
.''
R(CO
2
) is the ratio of CO
2
concentration to that prevailing in the pre-
industrial period (280 ppm) [R(CO
2
)
¼
CO
2
/280]. Royer et al. disputed these
conclusions. They claimed that prolonged cold intervals during the periods
460-400Myr and 220-120Myr, while R(CO
2
) was high, are unjustified. They also
disputed the validity of the ice volume effect, particularly during periods with no
glaciation. They concluded:
''The correspondence between the Phanerozoic records of atmospheric CO
2
and glacial sediments, and the revision of the
d
18
O paleo-temperature record
toward values better matching the glacial sediment record, strongly implicate
CO
2
as a primary driver of climate over these timescales. Cosmic ray flux is likely
only of second-order significance.''
Over roughly the same time period of the Shaviv/Veizer-Royer et al.
controversy, Wallmann (2004) developed a box model that included pH correc-
tions. He began with this introduction:
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