Global warming sparked by ancient farming methods

Ancient man may have started global warming through massive deforestation and burning that could have permanently altered the planet's climate, according to a new study by researchers at the University of Virginal and the University of Maryland-Baltimore County.

Published in the scientific journal Quaternary Science Reviews and reported on the University of Virgina's Web site, says over thousands of years, farmer burned down so many forests on such a large scale that huge amounts of carbon dioxide were pumped into the atmosphere.

Ruddiman said that starting thousands of years ago, people would burn down a forest, poke a hole in the soil between the stumps, drop seeds in the holes and grow a crop on that land until the nutrients were tapped out of soil. Then they would move on.

The slashing and burning on such a large scale spewed enormous amounts of greenhouse gasses into the atmosphere and warmed the Earth.

Ruddiman has studied and researched the idea of ancient man contributing to climate change for years now. And his endured plenty of criticism over his theories. Ken Calderia, a climate scientist at the Carnegie Institution's Department of Global Ecology in Standford, California, is among those who disagree with Ruddiman. He said Ruddiman is "exaggerating the importance of early man."

He said, "There are actually studies showing if you cut down forests for farmland, you actually cool the planet, because of the glare from the cleared land."

But Ruddiman said, "My argument is that even at the beginning, they just used much more land per person, so even though there weren't that many people, they used enough to start to push these greenhouse gas concentrations up."

Ruddiman's research also argues that the Earth was on its way to another ice age 10,000 years ago and that ice sheets were already forming in northern latitudes when ancient man started his slashing and burning method of farming.

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