Has climate change been around as long as the pyramids? It is an odd-sounding idea, because the problem is usually assumed to be a modern one, the product of a world created by the Industrial Revolution and powered by high-polluting fossil fuels. But a professor emeritus at the University of Virginia has suggested that people began altering the climate thousands of years ago, as primitive farmers burned forests and built methane-bubbling rice paddies. The practices produced enough greenhouse gases, he says, to warm the world by a degree or more. Other scientists, however, have said the idea is deeply flawed and might be used to dampen modern alarms over climate change. Understanding the debate requires a tour through polar ice sheets, the inner workings of the carbon molecule, the farming habits of 5,000-year-old Europeans and trapped air bubbles more ancient than Rome. "The greenhouse gases went up, and they should have gone down" many thousands of years ago, said U-Va.'s William Ruddiman. "Why did that happen?" His answer is based on circumstantial evidence. Ruddiman said two events in world history -- an apparent shift in the composition of the atmosphere and the first explosion of human agriculture -- took place at nearly the same time...WPost
HT: OzoneSky
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