"After a period of declining levels of belief in global warming there appears to be a modest rebound in the percentage of Americans that believe temperatures on the planet are increasing," according (PDF) to the latest National Survey of American Public Opinion on Climate Change.
Asked, "Is there solid evidence that the average temperature on Earth has been getting warmer over the past four decades," 62% of respondents said yes, 26% said no, and 12% said that they weren't sure. The 62% figure was a rebound: only 52%, 58%, and 55% of respondents said yes to the same question in spring 2010, fall 2010, and spring 2011, while 72% and 65% said yes in fall 2008 and fall 2009.
The report added, "partisanship continues to play a key role in predicting an American's views on the existence of global warming. While over 3 out of 4 Democrats indicate that there is solid evidence of climate change, Republicans are almost evenly [split] on the question, with 47% seeing evidence of increasing global temperatures and 42% contending that there is not enough evidence that the Earth is getting warmer. Contrary to the apparent partisan influence on perceptions of climate change, other traditional demographic categories such as gender, race and educational attainment offer little in the way of providing cues about an individual's standing on this issue."
Respondents who accepted global warming were also asked, "What is the primary factor that has caused you to believe that temperatures on earth are increasing?" Leading were personal observation of warmer temperatures and personal observation of extreme weather at 24% each; media coverage and scientific research trailed at 12% and 8%, respectively. Asked about factors that influenced their views, 56% cited declining glaciers and polar ice, 46% cited declining numbers of polar bears and penguins, and 43% cited extreme weather events; the comparatively less accessible factors of computer models and the IPCC reports trailed at 18% and 13%, respectively.
The report explained, "While Americans who think the planet is warming largely disagree with the premise that the media and climate scientists are overstating evidence about global warming, most citizens who do not see evidence of increasing temperatures on Earth believe that scientists and the press are distorting evidence on the matter." Among those respondents who accepted global warming, only 28% thought that scientists were overstating the evidence for their own interests and only 34% thought that the media is overstating the evidence; among those who rejected global warming, those figures precipitously rose to 81% and 90%, respectively.
The National Survey of American Public Opinion on Climate Change is jointly produced by the Gerald Ford School of Public Policy at the University of Michigan and the Muhlenberg College Institute of Public Opinion. The latest survey was conducted among 887 residents of the United States between December 4 and 21, 2011, by land and cell phones. According to the report, "The total number of completions results in a margin of error of +/- 3.5% at the 95% confidence interval. ... The data has been weighted by the following categories: age, gender, educational attainment, race and region."