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American Association for the Advancement of Science

New 'time machine' from ice

Thanks to air bubbles trapped in a long cylinder of ice from a glacier in Antarctica, scientists have jumped an extra 210,000 years back in time. This scientific "time machine" now tells us how much carbon dioxide and methane was in the air as far back as 650,000 years ago.

Carbon dioxide and methane are two important greenhouse gasses that trap heat and can contribute to global warming.

The full name of the ancient tube of ice is the "EPICA Dome C ice core." It contains hundreds of thousands of years of air samples within tiny bubbles trapped in the ice. The air bubbles form when snowflakes fall. Each bubble contains a record of how much carbon dioxide and methane was in that air at a specific time in the past.

Today's rising level of carbon dioxide in the atmosphere is already 27 percent higher than its highest recorded level during the last 650,000 years, said Science author Thomas Stocker of the Physics Institute of the University of Bern, in Bern, Switzerland.

Stocker explained that this research adds another piece of information showing that humans have changed the concentrations of some gasses in the air much faster than these gas levels have changed in the more distant past.

The scientists compared the new record of carbon dioxide and methane from 390,000 to 650,000 years ago to the history of Antarctic temperature for the same time period. This comparison confirms previous reports of a steady relationship between Antarctic climate and carbon dioxide and methane during the last four ice ages and the warm periods in between the ice ages. The new ice core research also extends this steady relationship back another 210,000 years (two ice ages and two warm periods).

Knowing how long the greenhouse gasses and Antarctic climate have been "going steady" may help scientists predict how the climate will change in the future, the scientists say.

Discovering the history of gasses in the air is also useful for trying to answer all sorts of other questions, like, when did humans start changing the levels of gasses in Earth's atmosphere? And, how long might our current warm period last?

This research appears in two papers in the 25 November 2005 issue of the journal Science.