Studying the Pliocene Paradox


Environmental conditions during the early Pliocene, 3 to 5 million years ago, were similar to and also very different from those of today. The intensity of sunlight incident on Earth, the global geography, and the atmospheric concentration of carbon dioxide were close to what they are today, but surface temperatures in polar regions were so much higher that continental glaciers were absent from the Northern Hemisphere, and sea level was 25 m higher than today. This apparent paradox–that the climate state of today is different from that during the early Pliocene despite the same external forcing, has been examined in a paper published in the June 9 issue of Science. According to the team of authors, lead by a PI sponsored by the Office of Science, the study has implications for future climate: a future melting of glaciers, changes in the hydrological cycle, and a deepening of the thermocline could restore the warm conditions of the early Pliocene.


Richard A. Kerr: PALEOCLIMATOLOGY: Looking Way Back for the World’s Climate Future. Science 9 June 2006: 1456-1457.

A. V. Fedorov, P. S. Dekens, M. McCarthy, A. C. Ravelo, P. B. deMenocal, M. Barreiro, R. C. Pacanowski, S. G. Philander. The Pliocene Paradox (Mechanisms for a Permanent El NiƱo) Science, 312, 1485-1489.