Encouraging news about the level of public acceptance of climate change in the United States is at hand. The executive summary of Climate Change in the American Mind: Americans' Global Warming Beliefs and Attitudes in September 2012 reports (PDF), "For the first time since 2008, more than half of Americans (54%) believe global warming is caused mostly by human activities." Moreover, "[f]or the first time since November 2008, Americans are more likely to believe most scientists agree that global warming is happening than believe there is disagreement on the subject." (The report provides longitudinal data back to November 2008.)
Presented with a definition of global warming as "the idea that the world's average temperature has been increasing over the past 150 years, may be increasing more in the future, and that the world's climate may change as a result" and asked whether they thought that global warming is happening, 70% of respondents said yes, while 12% said no and 18% indicated that they didn't know. Asked about the cause of global warming, on the assumption that it is happening, 54% of respondents said that global warming is caused mostly by human activities, while 30% said that it is caused mostly by natural changes in the environment, 6% volunteered that it is caused by both human activities and natural changes, 7% opted for "none of the above because global warming isn't happening," and 2% offered other views.
Asked for their views about what scientists believe, 44% of respondents agreed that most scientists think that global warming is happening, while 3% agreed that most scientists think global warming is not happening, 36% agreed that there is a lot of disagreement among scientists about whether or not global warming is happening, and 18% said that they don't know enough to say. Respondents were also asked how much they trust or distrust various sources of information about global warming. Climate scientists were strongly trusted by 25%, somewhat trusted by 51%, somewhat distrusted by 13%, and strongly distrusted by 6% of respondents, and the report comments, "Three out of four Americans (76%) say they trust climate scientists as a source of information about global warming, making them the most trusted source asked about in the survey."
The study was conducted by the Yale Project on Climate Change Communication and the George Mason University Center for Climate Change Communication. The surveys were administered from August 31, 2012, to September 12, 2012, using an on-line research panel of 1061 American adults. According to the report, "The sample ... includes a representative cross-section of American adults — irrespective of whether they have Internet access, use only a cell phone, etc. Key demographic variables were weighted, post survey, to match US Census Bureau norms." The margin of sampling error was plus or minus 3% at the 95% confidence level.