Myth: Carbon dioxide doesn't cause global warming

There has been some evidence from at least three Antarctic ice cores studies that show there was a lag time of around 800 years between the Earth’s temperature rising and global carbon dioxide levels rising at the end of the last Ice Age. The rise in temperature was a period of pronounced warming that marked the end of the ice age. From this data climate change sceptics have concluded that large levels of carbon dioxide do not cause global warming.

However this is an incorrect conclusion to make, as the warming period took around 5000 years to complete and the lag was only 800 years. This means that out of the 5000 years the first 800 years of warming wasn’t caused by carbon dioxide but the remaining 4200 could have been.

The exact cause of the initial warming of the planet is unknown but scientists do know that changes in the Earths orbit around the sun every 21,000 years affects the levels of summer sunshine which determines the start and end of Ice Ages.

Once the warming was underway and carbon dioxide levels were rising a feedback loop was formed where the rise in temperature became faster and faster as the increase in carbon dioxide trapped more and more heat which in turn generated the release of more carbon dioxide.

This means that although carbon dioxide did not start the glacial warming, it did amplify the heating process once it was underway.

From model estimates carbon dioxide and other greenhouse gases like methane and nitrous oxide are thought to have caused about half of the full glacial-to-interglacial warming.

Ice core study links:

http://icebubbles.ucsd.edu/Publications/CaillonTermIII.pdf

http://www.ncdc.noaa.gov/paleo/taylor/indermuehle00grl.pdf

Antarctic Peninsula glacier