At the American Geophysical Union meeting in San Francisco last December [climatologist James Hansen] named a number: 350 parts per million carbon dioxide.
That, he said, was the absolute upper bound of anything like safety — above it and the planet would be unraveling. Is unraveling, because we're already at 385 parts per million.
Bill McKibben writing about the 350 climate change campaign in the July | August 2008 issue of Orion Magazine.
