Low CO2, global cooling linked

A new Yale study adds to the body of evidence that climate change is connected to carbon dioxide.

Atmospheric carbon dioxide levels dropped shortly before ice formed in Antarctica 34 million years ago, according to a three-year study conducted by the Yale Department of Geology and Geophysics. The study’s results — which were published online Dec. 1 in the journal Science — indicate a relationship between levels of the gas in the atmosphere and climate change, said geology and geophysics professor Mark Pagani, the study’s principal investigator.

“It’s important to recognize these relationships,” Pagani said. “They have relevance to future climate change.”

Pagani said that researchers targeted the point about 34 million years ago when the planet shifted from a warmer, greenhouse climate to colder climate during which permanent ice shelves first formed in Antarctica.

The research team discovered that carbon dioxide levels decreased by a total of 40 percent over a three-million-year period before and during the beginning of the global cooling events, he said. Pagani added that this change in temperature caused a permanently new global climate and resulted in the formation and spread of ice in Antarctica, and the evolution towards our modern global climate system.

A U.S. government initiative called the Integrated Ocean Drilling Program, which acts as a repository for sediment material from drilling sites, provided the team with ocean core samples from six locations worldwide, he said. The composition of algae molecules in the rock was extracted from ancient strata and analyzed in order to reconstruct the carbon dioxide levels in the atmosphere, he said.

“Ocean sediments are our best continuous records out there of our history,” he said.

Pagani said the next goal of climate change research would likely involve modeling temperature changes in relation to ice volume and sea level changes.

University of Hawaii professor of oceanography Craig Smith, who has conducted climate change research in Antarctica in the past, stressed the importance of conducting studies of Antarctica, where historical data is more available.

“We can learn how climate change may affect other areas by looking at Antarctica,” he said. “We can get a preview, so to speak, of how things may be affected in other parts of the globe.”

The Earth’s atmospheric carbon dioxide levels have increased 37 percent since 1800.

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