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Science 7 April 2006:
Vol. 312. no. 5770, p. 15
DOI: 10.1126/science.312.5770.15m
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This Week in Science
During the early Pliocene epoch (5 million to 3 million years ago), there was little or no permanent ice in the Northern Hemisphere, and global mean surface temperatures were several degrees centigrade warmer than today. Around 3 million years ago, permanent continental ice sheets began to form in the Northern Hemisphere and the variability of high-latitude climate increased dramatically. How these changes are related to corresponding changes in tropical climate change has been a topic of vigorous debate. Lawrence et al. (p. 79) present a 5-million-year record of sea surface temperature and productivity variations from the eastern equatorial Pacific Ocean and find that cooling began about 4 million years ago, long before the intensification of Northern Hemisphere glaciation. Thus, high-latitude processes in the Southern Hemisphere helped drive ocean surface conditions in the eastern equatorial Pacific during the Pliocene and Pleistocene.
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Science. ISSN 0036-8075 (print), 1095-9203 (online)
