Only 57% of Americans feel that the planet's atmosphere is warming, a fall from 77% two years ago

The number of Americans who believe in global warming has plummeted, falling 20% in two years, a survey said today.

Only 57% of Americans believe there is solid scientific evidence that the Earth's atmosphere is warming, said the poll of 1,500 people by the Pew Research Centre for the People & the Press.

That is a fall of 77% from 2007. The number of people who believe that human activity is causing global warming also fell to just 36%.

The public uncertainty about the evidence behind global warming comes as the Senate prepares to begin debate next week on climate change legislation. Yesterday, 18 scientific organisations wrote Congress to reaffirm the consensus behind global warming.

Michael Dimock, the associate director of the Pew Centre, said the economic crisis and the struggles over healthcare reform had squeezed out climate change and the environment as issues of concern. "The public is just not as focused on global warming and environmental [issues] as they have been in the past."

But James Hoggan, a PR executive and author of Climate Cover-Up, blamed an intense lobbying campaign against global warming legislation now before the Senate. "I would say a big part of this problem is this campaign to mislead Americans about climate science," he said. "This is a very sophisticated group of people who know how to create doubt and confusion and they have done a very good job of it."



The decline was sharpest among independent voters and Republicans. Republicans in Congress have almost uniformly lined up against climate change legislation. There were also regional differences, with people in the mid-west and Rocky mountain states less inclined to see climate change as a serious problem.

But the perceived lack of concrete evidence for global warming did not necessarily hurt the prospects of voting on climate change legislation, Dimock said. Half of Americans polled remain in favour of putting limits and carbon emissions and making companies pay for their emissions -- the basics of the cap and trade bill now before the Senate.

A majority, 56%, also want America to join other countries in a global agreement on climate change.