The national survey by Yale and George Mason universities found the percentage of Americans who think global warming is happening has declined 14 points, to 57 percent, and the number of people who think global warming is caused mostly by human activities dropped 10 points, to 47 percent.
Coupled with those beliefs, researchers found an increase in the number of Americans who think global warming will never harm humans or other species.
"Despite growing scientific evidence that global warming will have serious impacts worldwide, public opinion is moving in the opposite direction," said Anthony Leiserowitz, director of the Yale Project on Climate Change.
The survey also found 40 percent of the public now believe there is much disagreement among scientists over whether global warming is happening.
"The scientific evidence is clear that climate change is real, human-caused and a serious threat to communities across America," said Edward Maibach, director of the Center for Climate Change Communication at George Mason University. "The erosion in both public concern and public trust about global warming should be a clarion call for people and organizations trying to educate the public about this important issue."
The Dec. 23-Jan. 3 survey of 1,001 U.S. adults carries a margin of error of 3 percentage points.
The report is available at: http://www.climatechangecommunication.org/images/files/CC_in_the_American_Mind_Jan_2010.pdf.