The Chronicle Review

Global Warming Before Smokestacks

Did humans start changing the climate thousands of years ago?

Michael Yamashita, Aurora Photos

Millennia ago, did just a few farmers—similar to these in present-day Yunnan, China—change the course of global climate?
November 01, 2009 Premium content for subscribers. Subscribe Today

People have changed the planet's climate, warming the atmosphere by churning out greenhouse gases.

But that process didn't start during the Industrial Revolution. It began thousands of years ago, according to a controversial hypothesis, before anyone...

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