The astronomical theory and data compared - Ice Ages and Interglacials: Measurements, Interpretation, and Models - page 276

with the variability of isotope ratios dicult to interpret. Several simple models
have been developed (as discussed in Section 9.6).
Maslin and Ridgwell (2005) used the term ''Mid-Pleistocene Revolution''
(MPR) to describe the transition from glacial-interglacial cycles of length 41,000
years to roughly 100,000 years which occurred about one million years ago.
They pointed out that eccentricity is often assumed to be the primary driver of
post-MPR climate cycles. They called this the ''eccentricity myth''.
Lisiecki and Raymo (2005) were able to produce a change in the period of
cycles within the Imbrie model by using different parameters for the early, middle,
and late periods (see discussion above Figure 5.1 in Section 5.2). However, this
seems to fall into the realm of curve fitting rather than physical reasoning.
10.2.1 Direct comparison of the variability of peak solar intensity with ice core data
The last ice age
Figure 10.1 presents a comparison of smoothed Greenland temperature with
yearly solar input at 65 N over the past 150,000 years. In the lower graph repre-
senting solar input to 65 N, curve A shows a rise in solar intensity that overlaps
with the evolution of the Eemian interglacial. However, the time period from 145
Figure 10.1. Comparison of smoothed Greenland temperature with yearly solar input at noon
at 65 N over the past 150,000 years.