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BOB HIRSHON (host):
Primitive climate change. I’m Bob Hirshon and this is Science Update.
Humans may have affected Earth’s climate thousands of years ago – by burning forests for farming. This according to a University of Virginia climate scientist William Ruddiman. He notes that about five or six thousand years ago, greenhouse gases mysteriously increased in the atmosphere. He also says that although there were far fewer people on the planet back then, they consumed up to ten times as much land per person as we do today.
WILLIAM RUDDIMAN (University of Virginia):
And that larger use of land means that tens of millions of people actually have the effect of hundreds of millions of people.
HIRSHON:
… Enough, he argues, to explain the spike in greenhouse gases – if you account for all the consequences of that slash-and-burn farming. If he’s right, then today’s more drastic climate change may have piggybacked on a smaller warming effect from long ago. I’m Bob Hirshon for AAAS, the Science Society.