An anonymous reader writes, "We've known since 2004 that the past 440,000 years have shown atmospheric carbon dioxide levels varying between about 200 and 300 ppmv, the difference in extremes being the difference between advancing ice sheets and our current clime. In 2005 the data were analyzed back to 650,000 years and were found to be much the same — Al Gore was proud to be able to show that then-new analysis in his 2006 movie An Inconvenient Truth. Now all 800,000 years of the ice column have been analyzed, and the data show much the same pattern, according to the researcher: 'When carbon dioxide changed there was always an accompanying climate change. Over the last 200 years human activity has increased carbon dioxide to well outside the natural range' — to 380 ppmv."
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