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New measurements of air bubble in Antarctic ice suggest that global warming was not started with the Industrial Revolution; scientists believe that global warming began during the agricultural Revolution. As humans began to cut down trees and other plants in order to make room for the crops they would plant, carbon dioxide levels began to rise and then 3,000 years later, methane levels began to rise as well. As this started happening, the earth's atmosphere began to become warmer and temperature levels began to rise. In earlier times, scientists believe that the onset of the earth's temperature rising came with the factories and industrialization in the 1800's, but more recent research has proven that it began naturally. Although levels of carbon dioxide and methane change naturally with the orbit of the earth, these gases are becoming more predominant throughout the atmosphere than they would naturally. New evidence proves that global warming started with the agricultural revolution thousands of years ago.

Bridges, A. Global Warming: 8,000 years ago. CBS News. Retrieved February 22, 2008, fromhttp://www.cbsnews.com/stories/2003/09/23/tech/main574644.shtml