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Study confirms strong link between CO2 and climate over 70,000 years
mongabay.com
September 11, 2008


Analysis of ice core samples from Greenland show a strong correlation between atmospheric carbon dioxide levels and abrupt changes in climate, reports a paper published in Science.

Comparing records of carbon dioxide concentrations, Antarctic surface temperatures, and Greenland's climate between 20,000 and 90,000 years ago, Jinho Ahn and Edward J. Brook found a close link between past climate change and CO2 levels. The researchers say the findings "appear to confirm the validity of the types of computer models that are used to project a warmer climate in the future," according to a statement from Oregon State University.

"We've identified a consistent and coherent pattern of carbon dioxide fluctuations from the past and are able to observe the correlation of this to temperature in the northern and southern hemispheres," said Ed Brook, an associate professor of geosciences at Oregon State University. "This is a global, interconnected system of ocean and atmosphere, and data like these help us better understand how it works."

Ahn and Brook say their work confirms that before humans, atmospheric carbon dioxide was largely controlled by oceanic processes. Now that anthropogenic activities are pumping significant amounts of CO2 into the atmosphere and potentially slowing marine overturning circulation, oceans may contribute positive feedback to the system, further increasing carbon dioxide levels, they write. The development could drive rapid shifts in climate.

"Before humans were affecting the Earth, what we are finding is regular warm and cold cycles, which both began and ended fairly abruptly," Brook explained. "This study supports the theory that a key driver in all this is ocean currents and circulation patterns, which create different patterns of warm and cold climates depending on the strength of various parts of the global ocean circulation system."

"In every historic sequence we observed, the abrupt warming of Greenland occurred about when carbon dioxide was at maximum levels," Brook continued. "And that was during an Ice Age, and at levels of atmospheric carbon dioxide that are far lower than those we have today."

Jinho Ahn* and Edward J. Brook. Atmospheric CO2 and Climate on Millennial Time Scales During the Last Glacial Period. SCIENCE 11 September 2008.