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CO2 levels tightly linked with climate change over past 420 million years
mongabay.com
March 28, 2007


New research shows that sensitivity of Earth's climate to changes in the greenhouse gas carbon dioxide (CO2) have been relatively consistence for at least 420 million years, suggesting that presently rising levels of carbon dioxide resulting from fossil fuel use will indeed produce higher temperatures in the future.

The study, published in the current issue of the journal Nature by scientists geologists at Yale and Wesleyan Universities, found that during the past 420 million years, each doubling of atmospheric CO2 translates to an average global temperature increase of about 3° Celsius, or 5° Fahrenheit.

Dana L. Royer of Wesleyan, together with Robert Berner and Jeffrey Park at Yale, used recent proxy measurements of CO2 to develop a historical record of the relationship between temperatures and atmospheric concentrations of the gas.

Recent rise in atmospheric CO2 levels CO2 emissions by country, click to enlarge

"Proxy data are indirect measurements of CO2 — they are a measure of the effects of CO2," said Dr. Park, professor of geology and geophysics at Yale who created the computer simulations for the project. "While we cannot actually measure the CO2 that was in the atmosphere millions of years ago, we can measure the geologic record of its presence. For example, measurement of carbon isotopes in ancient ocean-plankton material reflects atmospheric CO2 concentrations."

"Our results are consistent with estimates from shorter-term records, and indicate that climate sensitivity was almost certainly greater than 1.5, but less than 5.5 degrees Celsius over this period," said Park. "At those extremes of CO2 sensitivity, [1.5°C or 5.5°C] the carbon-cycle would have been in a 'perfect storm' condition."

Present CO2 levels are higher at any point than in the past 650,000 years according to a study published in the journal Science in November 2005.

Related

Atmospheric carbon dioxide levels closely correlated with global. Studying ice cores from Antarctica, scientists of the Alfred Wegener Institute for Polar and Marine Research extended the record of historic concentrations of carbon dioxide, methane and nitrous oxide in the atmosphere by 250,000 years. The team found a close correlation between atmospheric carbon dioxide levels and global temperatures. Over the past 650,000 years, low greenhouse gas concentrations have been associated with cooler conditions.



This article is based on a news release from Yale

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