(Warm interglacial periods / Cold glacial periods) are longer in duration.

• A. Warm interglacial periods
• B. Cold glacial periods
• C. Both equally
• D. Neither

Answer: (B)

Cold glacial periods last longer because once large ice sheets cover much of the land, the climate tends to stay locked in by strong feedbacks. The bright, expansive ice increases Earth's albedo, reflecting more sunlight and keeping temperatures low. Lower atmospheric CO2 during glacials weakens the greenhouse effect, reinforcing the cold state. It takes a long time for these effects to unwind as orbital forces only periodically nudge the system toward warming. When summer insolation rises enough to melt ice, CO2 released from the oceans amplifies the warming and helps end the glacial, but the interglacial phase that follows remains shorter than the lengthy cold spell that preceded it.