Ice core data - Ice Ages and Interglacials: Measurements, Interpretation, and Models - page 152

Figure 4.18. Comparison of d 18 O at several Antarctic sites. Dashed curves are for the present
interglacial (use time scale at bottom) and solid curves are for the previous interglacial (use time
scale at top). EDC ¼ Epica Dome C. EDML ¼ EPICA Dronning Maud Land.
implies ''that the equilibrium response of sea level to 1.5-2 C of global warming
could be an increase of 7-9 meters.'' They didn't seem to see that there is a logical
impasse here. If changes in CO 2 concentration accompany glacial-interglacial
transitions, why indeed did the CO 2 concentration not rise sharply above 300 ppm
during warmer interglacials? And if rising CO 2 toward 400 ppm has produced the
modest global warming of the past century, how is that connected to the warming
of past interglacials when CO 2 remained below 300 ppm? Nor did they consider
the possibility that the present interglacial has not yet reached its maximum tem-
perature independent of CO 2 , and perhaps (who knows?) is now extending
temperatures upward to emulate previous interglacials regardless of CO 2 .
Ultimately, the relationship between CO 2 concentration and global temperature
remains poorly understood.
Tzedakis et al. (2009) attempted to characterize the various interglacials of the
past 800,000 years. As they discussed, there is no airtight procedure for defining
when a given period is an interglacial. They took data from Figure 4.19 and