qDuring the deglaciation interval between 17,000 and
6,000 years ago, climate changes were driven by rising summer insolation
and by increased concentrations of CO2 in the atmosphere.
qBy 10,000 years ago, the angle of tilt of Earth’s axis
had reached a maximum at the same time that Earth’s
precessional motion moved it closest to the Sun on June 21. These combined orbital
effects produced a summer insolation maximum at all latitudes of the
northern hemisphere.
qAs the ice sheets shrank, their ability to influence
climate diminished.