In 2007, 62 percent of Republicans said there was solid evidence, but then the percentage slid for two years to 35 percent in 2009 before beginning to move up again.
“The percentage of Republicans saying there is solid evidence of warming is still lower than it was in 2006 and 2007, but is now about where it was in 2008,” a summary of the poll states.
There has been a similarly V-shaped trend for Democrats and Independents over the last six years, with belief in warming still below 2006 levels, but above the recent floor reached in 2009.
The poll is also the latest to show major divides between supporters of President Obama and GOP nominee Mitt Romney on climate change.
Eighty-eight percent of Obama voters see solid evidence of global warming compared with 42 percent of Romney backers. And among Obama backers, 59 percent call global warming a “very serious” problem, compared to 13 percent of Romney’s voters, Pew found.
The vast majority of scientists and scientific groups say global warming is occurring and that human activities — including the use of fossil fuels — are a major reason why.
The National Research Council, in a report last year, noted that climate change is “very likely caused primarily” by human-induced greenhouse gas emissions.
In 2009, 18 scientific groups — including the American Association for the Advancement of Science and the American Meteorological Society — issued a joint statement on the matter. They said that greenhouse gases emitted by human activities are the “primary driver” of climate change.
Sixty-three percent of Obama voters say global warming is occurring mostly because of human activity, compared to 18 percent of Romney voters, Pew found. Similarly, the poll shows that Democrats in general are far more likely than Republicans to blame warming on human activities.
The Pew data is available here. The poll of 1,511 people was conducted Oct. 4-7.
The margin of error for data about the whole group of people polled is plus-or-minus 2.9 percentage points. However, it’s around five percentage points for party-specific and candidate-specific answers, according to Pew.