Some 115 thousand years ago the world as we know it today shifted into a much colder glacial mode which culminated with huge ice sheets reaching as far south as New York, Berlin and St. Petersburg. The numerical climate models, used to predict the next century climate, were as yet unable to explain what happened. The reader of the book gains a detailed picture of what is known on the most important episodes of the past climate history, what to expect during the transition into a glacial climate mode, and which aspects and elements of the climate system seem mostsusceptible to change. The climate modelers will realize that the long term history of natural climate variations may hold important clues to the mechanism of climate changes which should be taken in account if the near future CO2 rich climate have to be predicted with any degree ofreliability.