Current carbon dioxide levels also prevailed 15 mn years ago

Then "global temperatures were five to 10 degrees Fahrenheit higher than they are today, sea level was approximately 75 to 120 feet higher than today, there was no permanent sea ice cap in the Arctic and very little ice on Antarctica and Greenland," said Aradhna Tripathi, who led the study.

"Carbon dioxide is a potent greenhouse gas, and geological observations that we now have for the last 20 million years lend strong support to the idea that carbon dioxide is an important agent for driving climate change throughout earth's history," said Tripathi, who is an earth and space science professor at the University of California -Los Angeles (UCLA).

"A slightly shocking finding," Tripathi said, "is that the only time in the last 20 million years that we find evidence for carbon dioxide levels similar to the modern level of 387 parts per million was 15 to 20 million years ago, when the planet was dramatically different."

By analysing the chemistry of bubbles of ancient air trapped in Antarctic ice, scientists have been able to determine the composition of the earth's atmosphere going back as far as 8,00,000 years.

"We are able, for the first time, to accurately reproduce the ice-core record for the last 800,000 years - the record of atmospheric carbon dioxide based on measurements of carbon dioxide in gas bubbles in ice," Tripathi said. "This suggests that the technique we are using is valid."
"We report evidence for a very close coupling between carbon dioxide levels and climate. When there is evidence for the growth of a large ice sheet on Antarctica or on Greenland or the growth of sea ice in the Arctic Ocean, we see evidence for a dramatic change in carbon dioxide levels over the last 20 million years."

The study is slated for publication in the journal Science.

Link MSN