Nearly four out of five Americans now think temperatures are rising and that global warming will be a serious problem for the United States if nothing is done about it, a new Associated Press-GfK poll finds.

But only 45 per cent of those surveyed think U.S. President Barack Obama will take major action to fight climate change in his second term.

Belief and worry about climate change are inching up among Americans in general, but concern is growing faster among people who don't often trust scientists on the environment. In follow-up interviews, some of those doubters said they believe their own eyes as they've watched thermometers rise, New York City subway tunnels flood, polar ice melt and Midwestern farm fields dry up.

'Events are helping these people see what scientists thought they had been seeing all along.'—Jon Krosnick, Stanford University social psychologist and pollster

Overall, 78 per cent of those surveyed said they thought temperatures were rising and 80 per cent called it a serious problem. That's up slightly from 2009, when 75 per cent thought global warming was occurring and just 73 per cent thought it was a serious problem.

In general, U.S. belief in global warming, according to AP-GfK and other polls, has fluctuated over the years but has stayed between about 70 and 85 per cent.

Biggest jump among science doubters

The biggest change in the polling is among people who trust scientists only a little or not at all. About one in three of the people surveyed fell into that category.

Within that highly skeptical group, 61 per cent now say temperatures have been rising over the past 100 years. That's a substantial increase from 2009, when the AP-GfK poll found that only 47 per cent of those with little or no trust in scientists believed the world was getting warmer.

This is an important development because, often in the past, opinion about climate change doesn't move much in core groups — like those who deny it exists and those who firmly believe it's an alarming problem, said Jon Krosnick, a Stanford University social psychologist and pollster. Krosnick, who consulted with The Associated Press on the poll questions, said the changes the poll shows aren't in the hard-core "anti-warming" deniers, but in the next group, who had serious doubts.

"They don't believe what the scientists say, they believe what the thermometers say," Krosnick said. "Events are helping these people see what scientists thought they had been seeing all along."

Phil Adams, a retired freelance photographer from North Carolina, said he was "fairly cynical" about scientists and their theories. But he believes very much in climate change because of what he's seen with his own eyes.

"Having lived for 67 years, we consistently see more and more changes based upon the fact that the weather is warmer," he said. "The seasons are more severe. The climate is definitely getting warmer."

"Storms seem to be more severe," he added.

Global warming 'very serious,' say nearly half of respondents

Nearly half, 49 per cent, of those surveyed called global warming not just serious but "very serious," up from 42 per cent in 2009. More than half, 57 per cent, of those surveyed thought the U.S. government should do a great deal or quite a bit about global warming, up from 52 per cent three years earlier.

Only 45 per cent of Americans surveyed believe that U.S. President Barack Obama will take major action to fight climate change in his second term. (Robin Buckson/Pool/Associated Press)

Overall, the 78 per cent who think temperatures are rising is not the highest percentage of Americans who have believed in climate change, according to AP polling. In 2006, less than a year after Hurricane Katrina devastated New Orleans, La., 85 per cent thought temperatures were rising.

The lowest point in the past 15 years for belief in warming was in December 2009, after some snowy winters and in the middle of an uproar about climate scientists' emails that later independent investigations found showed no manipulation of data.

Broken down by political party, 83 per cent of Democrats and 70 per cent of Republicans say the world is getting warmer. And 77 per cent of independents say temperatures are rising. Among scientists who write about the issue in peer-reviewed literature, the belief in global warming is about 97 per cent, according to a 2010 scientific study.

The AP-GfK poll was conducted Nov. 29 to Dec. 3 by GfK Roper Public Affairs and Corporate Communications. It involved landline and cellphone interviews with 1,002 adults across the U.S. Results for the full sample have a margin of error of plus or minus 3.9 percentage points; the margin of error is larger for subgroups.