http://www.nytimes.com/2006/12/15/science/15climate.html

Research and fresh computer simulations considered under the new
review have greatly strengthened that link, while also closing in on a possible
warming of 5 degrees above the 1990 average, more or less, should the
concentration of carbon dioxide double from the longstanding peak measured
before the industrial era.


For at least 600,000 years before the Industrial Revolution, the concentration
of carbon dioxide rarely nudged beyond 280 parts per million. It is now 382
parts per million and rising steadily.


Without a worldwide shift to nonpolluting energy technologies, such a doubling
is considered almost unavoidable given the growth in such emissions in both
wealthy and developing countries, but particularly in China and India.