While 63% of Americans overall believe there is trustworthy evidence of global warming, there is a sharp partisan and ideological divide on the issue.
The national survey by the Pew Research Center for the People & the Press found out that nearly 77% Democrats think that global warming is happening compared to 43% of Republicans. Among Republicans, only 31% of conservatives believe in global warming, and nearly three-quarters of them (73%) declare global warming either is not too serious a problem or not a problem at all. 63% Republicans that consider themselves as moderate or liberal trust in climate change, even though they represent a smaller portion of the party than do conservatives.
There also is a large partisan gap in views about the causes of global warming: 51% of Democrats say the Earth is getting warmer mostly because of human activity. Just 19% of Republicans say rising temperatures are mostly owing to human activity.
Probably these are the reasons why in the 2012 Republican presidential primaries anthropogenic climate change and the challenges of global warming seem to fade away. The main candidates flip-flopped on questions about environment and economic development. And they in particular start to reject man-made global warming.
Speaking at Consol Energy Center in Pittsburgh, Pennsylvania, in October, Republican presidential candidate Mitt Romney, famous for his frequent flip-flops, reversed his earlier stance on climate change pollution and denied anthropogenic global warming. “We don’t know exactly what causes climate change,” he said, “so US should not throw away trillions and trillions of dollars to try to cut carbon dioxide emissions.” Romney concluded his speech saying that EPA wants to control all of energy to force prices to rise. In June, Romney’s advice was quite different; in New Hampshire he told that he believed in man-caused global warming, and that tackle greenhouse pollution was an important goal. “I believe that the world is getting warmer and warmer, and that humans contribute to that,” he declared.

When he was governor of Massachusetts, he planned to regulate carbon dioxide as a pollutant, and was advised by Dr. John Holdren, now President Obama’s scientific adviser. Now, if you look at his programme, he points to increase and exploit US domestic reserves of oil and natural gas and to invest in nuclear power.

What about the other major candidates?  In 2008, Ron Paul said to The New York Times that the science community was showing how human activity can influence current fluctuations in temperature (the question to establish was how much); he also declared that he wanted to stop subsidies for oil companies…but in 2009, after the first Climategate, he recognized the artificial panic around global warming as an elaborate hoax. Talking about “global warming terrorism”, he said that Copenhagen treaty can’t help the economy and the environment.
It seems more positive Newt Gingrich, another Republican candidate that even if he did not directly address the problem of climate change, would like to promote energy  production from all sources and finance cleaner energy research.
Something has changed: considering a “pre- and a post- Copenhagen”, fewer Americans say there is solid evidence of global warming than did so from 2006 to 2008. And in those years, higher percentages viewed global warming as a very serious problem than do so today.
Eventually, the final impression is that climate change impacts and formulas to cut carbon dioxide emissions are not a priority anymore in the Republican agenda.