With all the concern about global warming, it may be surprising to read that "today's climate is just a geologically short warm spell in a continuing ice age." In this lucid and informative book, Macdougall (A Short History of Planet Earth
), an earth science professor at the Scripps Institution of Oceanography, introduces some of the scientists who have studied the Earth's ice ages, including the celebrated 19th-century naturalist Louis Agassiz, who put forth the theory, revolutionary at the time, of a global ice age; the amateur scientist James Croll, who propounded the idea that cycles of glacial and interglacial climates are related to changes in Earth's orbit around the Sun; and J. Harlan Bretz, who studied the catastrophic glacial flood that produced the "Channeled Scablands" of Washington state. That glaciers once extended from the North Pole to the Mediterranean was a fact accepted only gradually, and Macdougall examines in detail the clues—rock formations, glacial deposits, fossils and sediment cores—that scientists have used to prove the existence of continental ice sheets, as well as to study them. He closes with a discussion of our current ice age, suggesting that global warming may bring it to a premature end. Some of the science can get a bit technical, but Macdougall's readable style makes it accessible to the interested layperson. Illus. not seen by PW
. Agent, Rick Balkin. (Oct.)
