Global Warming Most Likely Due to Human Activity

In its last report, published in 2001, the Intergovernmental Panel on Climate Change concluded that there was a 66 to 90 percent chance that human activities were driving the most recent climate warming. But in its most recent report, which will be released on 2 February, the panel revised its claim and said that it is more than 90 percent likely that global warming since 1950 has been driven mainly by the buildup of carbon dioxide and other heat-trapping greenhouse gases, and that more warming and rising sea levels are on the way.

Drafts of the report project a most likely warming of 4 to 8 degrees if the concentration of carbon dioxide in the atmosphere rises to twice the 280 parts per million that it averaged for many centuries before the Industrial Revolution.

The carbon dioxide concentration is now roughly 380 parts per million, and many climate experts say it will be extremely difficult to avoid hitting levels of 450 or 550 parts per million, or higher, later this century, given growth in populations and fuel use and the lack of nonpolluting alternatives that can be exploited at a sufficient scale to replace fossil fuels.

Keep in mind that this report is still undergoing revisions, and these details have been leaked to the press, so some of the information may change before the release date.

Cited story.

Image: Union of Concerned Scientists.

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