The astronomical theory and data compared - Ice Ages and Interglacials: Measurements, Interpretation, and Models - page 282

Figure 10.4. Comparison of Antarctic ice core data with calculated solar input at 65 N over
400,000 years: (upper panel) Vostok data; (lower panel) solar input to 65 N.
the decay of ice sheets. This model does not work perfectly at all times but it does
seem to fit the data to some extent. It would explain why the 22,000-year
precession frequency does not show up in the frequency spectrum of the ice core
time series.
A similar effect occurs with Vostok data over 400,000 years (as shown in
Figure 10.4 ). Temperature increases shown as paths 2, 4, 6, and 8 seem to be
associated with sharp upward oscillations in solar intensity, producing short-lived
(e.g., about half of the 22,000-year precession cycle) interglacial periods. However,
these are always followed by sharp downward oscillations in solar intensity that
begin new ice ages. Even though significant solar oscillations persist, once a down-
ward trend in temperature is established (and ice sheets form) the ice age deepens
along paths 1, 3, 5, and 7.