Climate Meddling Dates Back 8,000 Years. By Alexandra Witze, Science News, 3/29/11. “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 taken humanity eight millennia.)…

“[Team leader Jed Kaplan of the Federal Polytechnic School in Lausanne, Switzerland] reported the work on March 25 at an American Geophysical Union conference on past civilizations and climate. He and Lausanne colleague Kristen Krumhardt also describe the findings in an upcoming issue of Holocene… Climate scientists often select 1850 as the putative start of the industrial revolution. But the world in 1850 was not a pristine globe untouched by human hands... Rather, people cut down forests and cleared land early on... Previous research often assumed that as the world’s population grew, the proportion of cleared land grew as well. But the more people crowded onto a landscape, the more efficient they became at extracting dinner from it… Irrigation, fertilizer, multicropping and new tools allowed farmers to increase crop yields, and per-capita land use began to drop...

“Kaplan and Krumhardt looked at how growing population and changing land-use trends affected carbon emissions. The scientists gathered data on how many people lived in each population center for the past 8,000 years, then cataloged how land use changed over time. The result: a
dramatic video showing a green-forested world giving way to a brown spread of deforestation, up until the modern era.”

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