Climate meddling dates back 8,000 years

www.sciencenews.org

April 23rd, 2011; Vol.179 #9
By Alexandra Witze

SANTA FE, N.M. — People started influencing their home planet’s climate millennia before the industrial revolution’s fossil fuel–burning machines began spewing carbon dioxide and other heat-trapping gases into the atmosphere, a new study suggests.

Clearing land — first to hunt and gather, and then to farm — removed trees that otherwise would have soaked up carbon dioxide. The new work suggests that humans working the land put nearly 350 billion metric tons of carbon — many times other estimates — into the atmosphere by the year 1850. (For comparison, between 1850 and 2000 people added 440 billion tons of carbon, mostly from burning fossil fuels — surpassing in a century and a half what had previously taken humankind eight millennia.)

“Our data show very substantial amounts of human impact on the environment over thousands of years,” says team leader Jed Kaplan of the Federal Polytechnic School in Lausanne, Switzerland. “That impact really needs to be taken into account when we think about the carbon cycle and greenhouse gases.”

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