How Mongolian hordes reduced the Earth's carbon footprint

In the 1200s, Genghis Khan and the Mongolian army built an empire that stretched from the Pacific Ocean to central Europe, ruling over a fifth of all land on Earth and over 100 million people. And all that conquering reshaped the Earth, reducing carbon dioxide levels enough to offset a year's worth of gasoline usage… » 2/08/11 11:06am 2/08/11 11:06am