Nearly 40 percent of Americans are part of categories called the "alarmed" or "concerned," meaning they are more likely to say global warming is man-made and are motivated to do something about it.
At the opposite end of the ideological spectrum, there are the "doubtful" and "dismissive," -- the 25 percent of Americans who are more likely to express climate skepticism or doubt that climate change will ever harm them personally.
In the middle are two other categories of Americans: the "cautious" and the "disengaged," the 35 percent who either say there is little urgency to the problem or simply haven't thought about the issue at all.
Those findings came yesterday in a joint survey from Yale and George Mason universities, examining broadly how adults think about climate change and what policies they would back to curb warming temperatures.
"I think that people tend to divide others into 'believe' or 'do not believe,'" said Anthony Leiserowitz, director of Yale University's Project on Climate Change and a co-author of the report. "It is a much more complicated and interesting picture than that."
According to Leiserowitz, the aim with the documentation of the "Six Americas" is not to examine why people feel the way they do, but provide a more sophisticated tool of measurement and track it over time.
There are some "slight" demographic differences between the groups, with the "dismissives" being more likely to be white, male, religious and conservative, Leiserowitz said. The "alarmed" are somewhat more likely to be female, he said. But most differences between the six partitions are not explained by an obvious label such as age, ethnic group or economic status.
Overall, the researchers found that 47 percent of Americans say that global warming is "caused mostly by human activities," while 36 percent say that it is "caused mostly by natural changes in the environment." About 30 percent say they think there will be many more "deaths and injuries" from floods and hurricanes over the next 20 years if nothing is done to address climate change.
Twenty-eight percent say the United States should make a large-scale effort to address global warming, even if has large economic costs.
'A stabilizing of beliefs'
But when you break the numbers down within the "Six Americas," the picture is much more complex.
For example, 23 percent of Americans total say that global warming will harm people in developing countries a great deal. With the "alarmed," the number surges to 85 percent. For the "concerned" -- those who believe climate change is happening but are less urgently worried than the "alarmed" -- the percentage drops to 36 percent. Within the group that is sure global warming is not happening, "the dismissives," the percentage worried about harm to developing countries drops to zero.
The universities have been tracking the beliefs of the Six Americas since 2008, with little change in the overall percentages occurring between this year and last, Leiserowitz said.
The biggest shift in attitudes came between November 2008 and January 2010, when the number of "dismissives" more than doubled and the "alarmed" decreased by 8 points. That mirrored other polls showing a growth in climate skepticism over the same time frame, a phenomenon that has been explained by the economic crisis, weather and the "Climategate" scandal, which revealed scientists wrangling in hacked emails (ClimateWire, Dec. 3, 2009).
"What we see here is a stabilizing in belief from last year," said Leiserowitz. "The drop has stopped."