Science: Another Ice Age?

The arrival of another ice age has long been a chilling theme of science fiction. If the earth's recent history is any clue, says Marine Geologist Cesare Emiliani of the University of Miami, a new ice age could become a reality.

Writing in Science, Emiliani reports that the earth has undergone at least eight periods of extreme cold and seven of torrid heat in the past 400,000 years. His conclusion is based on cores of ocean sediment from the Caribbean. Composed of the remains of tiny sea animals, the layered sediment provides a record of climatic changes. When the oceans warm up,...