Nearly two-thirds of moderate or liberal Republicans believe there is solid evidence for global warming, Pew poll finds

This won't make the Koch brothers happy: nearly two-thirds of moderate or liberal Republicans now believe there is solid evidence for global warming, according to a poll from the Pew research centre.

That's 22 points higher since 2009, the year the billionaire oil brothers first began pouring money into Tea Party groups working to discredit Barack Obama's green agenda.

The shift suggests that the Koch efforts to spread doubt about climate science may be backfiring.

Climate change doubt – seen by Tea Party activists as a litmus test of conservative credentials – is not, as it turns out, energising the Republican masses.

It's dividing them, alienating from the Tea Party wing those more moderate Republicans who account for about a third of the party's supporters.

"The gap between conservative Republicans and the party's moderates and liberals has increased from nine percentage points in 2009 to 32 percentage points," Pew said.

That raises an interesting question ahead of the 2012 elections: how much more political mileage is there in climate change doubt?

About half of the new crop of Republicans elected to Congress for the first time in last year's mid-term elections denied the existence of climate change and were opposed to action on climate change, according to ThinkProgress, a blog run by the Centre for American Progress.

But they do not seem to have been able to spread the doubt much beyond their own hardcore constituency.

Among Tea Party supporters, Republican and Independent, only 30% see evidence of global warming and 11% accept it is manmade, according to the poll.

Among those opposed to the Tea Party, Republican and independent, a majority, 56%, see concrete proof of global warming and 28% say it is caused mainly by humans.

Among Americans overall the number of people who believe there is concrete proof of global warming rose to 63%, from 59% last year.

More than three-quarters of Democrats see evidence of climate change.

Among independents 63% believe in climate change, up 10 points from two years ago.

Some 38% of Americans believed the climate was changing because of human activity, a rise again over last year when 32% believed in manmade global warming.

The numbers of Americans are still not as high they were in 2006, the year Al Gore released his award-winning Inconvenient Truth documentary. At that time more than three-quarters, 77%, of Americans said they believed in climate change, and about half believed it was man-made. More than 40% viewed climate change as a very serious problem.

But the numbers are beginning to head back up from that great slough of denial of the last two years, when the Kochs began channelling more money to climate doubting thinktanks and astro-turf groups.

Except, that is, among conservative Republicans – the target audience of the Tea Party campaigns. Just 31% see clear evidence of climate change.

The poll, released on Wednesday, was conducted on 9-14 November among 2,001 adults.