Americans believe climate change is occurring, but disagree on why

Republicans most often point to natural causes of climate change while Democrats most often believe that human activities are the cause. The greatest polarization occurs among people who believe they have the best understanding.

"Although there remains active discussion among scientists on many details about the pace and effects of climate change, no leading science organization disagrees that human activities are now changing the Earth's climate. The strong scientific agreement on this point contrasts with the partisan disagreement seen on all of our surveys," said Lawrence Hamilton, professor of sociology and senior fellow with the UNH Carsey Institute.

"However, most people gather information about climate change not directly from scientists but indirectly, for example through news media, political activists, acquaintances, and other nonscience sources. Their understanding reflects not simply scientific knowledge, but rather the adoption of views promoted by political or opinion leaders they follow. People increasingly choose news sources that match their own views. Moreover, they tend to selectively absorb information even from this biased flow, fitting it into their pre-existing beliefs," Hamilton said.

A series of regional surveys conducted by Carsey Institute researchers in 2010 and early 2011 asked nearly 9,500 individuals in seven regions in the United States about climate change.

Key findings include:

• Most people say that they understand either a moderate amount or a great deal about the issue of global warming or climate change.
• Large majorities agree that climate change is happening now, although they split on whether this is attributed mainly to human or natural causes.
• Level of understanding about climate change varies considerably by region.
• Beliefs about climate change are strongly related to political party. Republicans most often believe either that climate is not changing now or that it is changing but from mainly natural causes. Democrats most often believe that the climate is changing now due mainly to human activities.
• Political polarization is greatest among the Republicans and Democrats who are most confident that they understand this issue. Republicans and Democrats less sure about their understanding also tend to be less far apart in their beliefs.
• People who express lower confidence also might be more likely to change their views in response to weather.

"If the scientists are right, evidence of climate change will become more visible and dramatic in the decades ahead. Arctic sea ice, for example, provides one closely watched harbinger of planetary change. In its 2007 report the IPCC projected that late-summer Arctic sea ice could disappear before the end of the 21st century. Since that report was written, steeper-than-expected declines have led to suggestions that summer sea ice might be largely gone by 2030, and some think much sooner," Hamilton said.

"We will find out in time -- either the ice will melt, or it won't. The Arctic Ocean, along with other aspects of the ocean-atmosphere system, presents an undeniable physical reality that could become more central to the public debate. In the meantime, however, public beliefs about physical reality remain strikingly politicized," he said.

The complete report about this research is available at http://www.carseyinstitute.unh.edu/publications/IB-Hamilton-Climate-Change-2011.pdf.

This research was supported by grants from the Ford Foundation, Kellogg Foundation, Neil and Louise Tillotson Fund, New Hampshire Charitable Foundation, Office of Rural Development in the U.S. Department of Agriculture, UNH Sustainability Academy, and the Carsey Institute. The UNH Survey Center conducted all telephone interviews.