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09 Oct 2009: Current CO2 Levels
May Be Highest in 15 Million Years

A new study suggests that concentrations of carbon dioxide in the earth’s atmosphere are higher now than they have been in 15 million years. Reporting in the journal Science, U.S. researchers said that by studying the shells of ancient marine algae, they were able to determine that the last time CO2 levels were this high occurred 15 to 20 million years ago when the earth was 5 to 10 degrees hotter, sea levels were 75 to 120 feet higher, and there was no permanent ice cap in the Arctic. Until now, the best available climate record — obtained by examining ice bubbles in Antarctic ice cores — showed that concentrations of CO2 in the atmosphere are higher today than at any time in the past 800,000 years. If the research by Arhadhna Tripati of the University of California at Los Angeles proves correct, that would mean that science has been able to extend the climate record much farther into the past. Tripati and her colleagues determined CO2 levels in the algae shells by studying the ratio of the chemical element boron to calcium, and Tripati reported that her findings matched the overall CO2 trends seen in Antarctic ice cores. She called her findings “slightly shocking” and said that if CO2 levels, now at 387 parts per million, keep going up, the earth could be in store for the high temperatures and major sea level rises of the Middle Miocene period 15 million years ago.

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