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November 28, 2005
Volume 83, Number 48
p. 7

Climate Change

Ice Core Record Extended

Analyses of trapped air show current CO2 at highest level in 650,000 years

Bette Hileman

Courtesy of Laurent Augustin/Laboratoire de Glaciologie et Géophysique de l'Environnement

Icy Depths Drill head and ice core from a depth of 2,874 meters at Dome C Station in East Antarctica. This core is about 491,000 years old. The entire 3,270-meter ice core drilled at Dome C contains a continuous record of greenhouse gases for the past 650,000 years.

Ice cores drilled at vostok Station in East Antarctica provide evidence of Earth's temperatures and greenhouse gases for the past 440,000 years. Now, data from a new ice core called EPICA Dome C, drilled roughly 600 miles from Vostok, extends that record back another 210,000 years.

A study by Thomas F. Stocker of the Physics Institute at the University of Bern, in Switzerland, and colleagues describes Dome C core data that reveal the relationship between global temperatures and atmospheric carbon dioxide concentrations for the period 390,000 to 650,000 years before present (Science 2005, 310, 1313). The data indicate that the current concentration of CO2, at 380 ppm, is 27% higher than the preindustrial level and higher than any level attained during the past 650,000 years.

A second study based on Dome C data, a