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 Earth's climate, according to a new study by researchers at the University of Virginia and the University of Maryland-Baltimore County.

The study, published in the scientific journal Quaternary Science Reviews and reported on the University of Virginia's Web site, says over thousands of years, farmers burned down so many forests on such a large scale that huge amounts of carbon dioxide were pumped into the atmosphere. That possibly caused the Earth to warm up and forever changed the climate.

Lead study author William Ruddiman is a professor emeritus of environmental sciences at the University of Virginia and a climate scientist. "It seems like a common-sense idea that there weren't enough people around 5, 6, 7,000 years ago to have any significant impact on climate. But if you allow for the fact that those people, person by person, had something like 10 times as much of an effect or cleared 10 times as much land as people do today on average, that bumps up the effect of those earlier farmers considerably, and it does make them a factor in contributing to the rise of greenhouse gasses," Ruddiman said.