http://www.scientificamerican.com/artic ... of-climate
Three-Quarters of Climate Change Is Man-Made
An independent study quantifies the human and natural contributions, with solar radiation contributing only minimally
Natural climate variability is extremely unlikely to have contributed more than about one-quarter of the temperature rise observed in the past 60 years, reports a pair of Swiss climate modelers in a paper published online December 4. Most of the observed warming—at least 74 percent—is almost certainly due to human activity, they write in Nature Geoscience.