Unraveling the Signals of Global Climate Change

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Science  14 Jan 2000:
Vol. 287, Issue 5451, pp. 246-247
DOI: 10.1126/science.287.5451.246

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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.