Here's a doc that goes over the history of the idea of rapid temperature changes in the Earth's climate: Rapid Climate Change I'm not sure it directly answers your question. read more
During the present ice age, glaciers have advanced and retreated over 20 times, often blanketing North America with ice. Our climate today is actually a warm interval between these many periods of glaciation. The most recent period of glaciation, which many people think of as the "Ice Age," was at its height approximately 20,000 years ago. read more