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Science 14 January 2000:
Vol. 287. no. 5451, pp. 246 - 247
DOI: 10.1126/science.287.5451.246
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Perspectives

GEOSCIENCE:
Unraveling the Signals of Global Climate Change

Gary S. Dwyer

During the last 50 million years, Earth's climate has been getting colder. An important measure of this trend can be found in data on the concentration of oxygen isotopes in the fossil shells of tiny sea creatures. Yet, as Dwyer discusses in his Perspective, the isotope record has been plagued by a vexing ambiguity: the relative contribution of changes in ocean temperature and in the volume of polar ice are intertwined. Now, in a report in the same issue Lear et al. describe a new method for resolving the ambiguity. By measuring the ratio of magnesium to calcium in the microfossils, the temperature effect can be separated from the ice volume effect. While challenges remain to a full understanding of the climate record, the new findings clearly indicate the potential of this new analysis tool.

The author is at the Division of Earth and Ocean Sciences, Duke University, Durham, NC 27708. E-mail: gdwyer{at}eos.duke.edu

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Science. ISSN 0036-8075 (print), 1095-9203 (online)