This book tells the exciting story of the ice ages--what they were like, why they occurred, and when the next one is due. The solution to the ice age mystery originated when the National Science Foundation organized the CLIMAP project to study changes in the earth's climate over the past 700,000 years. One of the goals was to produce a map of the earth during the last ice age. Scientists examined cores of sediment from the Indian Ocean bed and deciphered a continuous history for the past 500,000 years. Their work ultimately confirmed the theory that the earth's irregular orbital motions account for the bizarre climatic changes which bring on ice ages.

This is a tale of scientific discovery and the colorful people who participated: Louis Agassiz, the young Swiss naturalist whose geological studies first convinced scientists that the earth has recently passed through an ice age; the Reverend William Buckland, an eccentric but respected Oxford professor who fought so hard against the ice-age theory before accepting it; James Croll, a Scots mechanic who educated himself as a scientist and first formulated the astronomic theory of ice ages; Milutin Milankovitch, the Serbian mathematician who gave the astronomic theory its firm quantitative foundation; and the many other astronomers, geochemists, geologists, paleontologists, and geophysicists who have been engaged for nearly a century and a half in the pressing search for a solution to the ice-age mystery.

This book details all the theories, and the history behind their development. From deep sea radiolarians, to terraced reefs in the equatorial regions, to vegetation studies in Europe, to the level of snow on Ethiopia's mountains, to axis and ellitpical variations in the earth's orbit, to the gravitational effect of the pull on the earth from other planets, to oxygen isotope studies, to graphs of variation in thermal energy, temperature and sea level at different lattitudes-both expected from Milankovitch cycles-and actual from deep sea analysis, this book pretty much covers all you need to know. The only drawback is it has missed a few recent ideas in the 1980s to 1990s, but the story was pretty much over by then. Pretty conclusive evidence is detailed on how regular and episodic variations in the earth's orbit around the sun trigger periodically cooler climates than at present. These have been particularly strong in the last 1.5 million years or so, which is thought to do with the configuration of recent continental geography. In the last 7,000 years the tmeperature has dropped around 2 degrees, and will continue to drop over the next several thousand years at least, albeit very slowly, if it wasn't of course for the already verified greenhouse warming. Unfortunately, being published in the late 1970s, the book has not captured much of the recent data and debate concerning the greenhouse effect, but is nevertheless an intriguing and enlightening expose of earth climate variations.

The other thing which struck me just a little, was the fact that the major ice age periods in the earth's past have been at or around 3 interesting changes or developments in evolutionary history-the Permo-Carboniferous (ie Permian-Triassic extinction), Pre-Cambrian (multicelled organisms), and Quaternary-Recent (hominids). Certianly the hominid succession has been mostly within major changes in the earths climate, including significantly colder periods, and vast ice sheets across northern lattitudes. Maybe coincidental, but something to think about.