qThe 23,000-year
cycle of orbital procession increases (decreases) summer insolation
and at the same time decreases (increases) winter insolation at low
and middle latitudes.
qDepartures from
the modern seasonal cycle of solar radiation have driven stronger monsoon
circulation in the past.
qGreater summer
radiation intensified the wet summer monsoon.
qDecreased winter
insolation intensified the dry winter monsoon.