'Overwhelming' consensus for manmade warming

A review of thousands of studies published over 21 years found "overwhelming" and growing consensus among scientists that humans are mostly to blame for global warming, its authors said Thursday. This contradicts a widely held view that scientists are deeply divided on the topic -- a misconception that complicates efforts to win public backing for climate policy, the authors wrote in the journal Environmental Research Letters. "An accurate perception of the degree of scientific consensus is an essential element to public support for climate policy," they wrote. "Communicating the scientific consensus also increases people's acceptance that climate change is happening." Researchers from the United States, Australia and Canada reviewed more than 4,000 scientific papers that expressed a position on whether humans were mostly to blame for recent global warming. The papers, published between 1991 and 2011, were written by more than 10,000 scientists. Just over 97 percent agreed that manmade warming was a reality. "Our analysis indicates that the number of papers rejecting the consensus... is a vanishingly small proportion of the published research," the team wrote. In stark contrast, opinion polls conducted in the United States from 1997 to 2007 found that about 60 percent of Americans believed there to be significant disagreement among scientists. "Scientists overwhelmingly agree that the Earth is warming due to human activity," said the authors, who claim that their work is the most comprehensive review of its kind ever undertaken. "There is a significant gap between public perception and reality." The United Nations is targeting a maximum temperature rise of two degrees Celsius (3.6 degrees Fahrenheit) on pre-industrial levels, for what scientists believe would be manageable climate change. To this end, countries are negotiating curbs to emissions of Earth-warming greenhouse gases released by fossil fuel burning. Last week, the level of carbon dioxide in Earth's atmosphere breached a threshold of 400 parts per million -- a level never experienced by humans and considered the absolute maximum for the two-degree target to remain within reach.