By Alex Kirby
BBC News Online environment correspondent
Most US policymakers do accept that climate change is a significant threat, a leading British scientist believes.
The American climate experiences a huge range of temperatures
Professor John Schellnhuber, of the University of East Anglia, said he thought about 80% of senior politicians recognised the danger "in principle".
He said he thought this consensus would eventually lead to a change in policy by President Bush's administration.
Professor Schellnhuber was among a UK scientific delegation which held talks on climate recently in Washington DC.
He is research director of the UEA's Tyndall Centre for Climate Change Research, and was speaking to BBC News Online.
Professor Schellnhuber said: "We spoke to the Congressional scientific committee, and my feeling is that in principle 80% of the people in Washington who are really informed feel dramatic climate change is a major threat.
"The administration is a prisoner of its own determination not to do anything that would affect the lifestyle of US citizens.
"Perhaps, in a parallel with its stance on Iraq, it has chosen a certain position and will now not alter it for fear of losing face.
"I don't think the US public and policymakers will be happy to go on with a business-as-usual approach for the next five years.
"I'm a scientist, not a politician. But I think the political elite understands pretty well what is going on, and the administration will eventually change."
Professor Schellnhuber, formerly the German government's chief environmental adviser, welcomed a report prepared by the Pentagon which warns of the potentially disastrous consequences of climate change to Europe within decades.
He said: "It's old stuff, about the possible collapse of the thermohaline circulation which keeps the Gulf Stream flowing to north-west Europe.
"If that stopped, average temperatures in countries like the UK could drop by about five degrees.
"It's a possible 'tipping point', a critical stage in global warming. But it's only one such point.
"I try to tell politicians about a range of them - that the Indian monsoon could change, or the Sahara become green again, or the Amazon forests disappear.
"I think the Pentagon didn't grasp the full complexity of what could happen and focused just on this, because the US is much more worried about possible cooling than about warming.
"We've been telling politicians for 20 years that climate change could be a far worse threat than terrorism.
"Unfortunately, our scientific assessments indicate that the window of opportunity for intervention to protect the climate is closing rapidly.
"In fact, we may have missed certain opportunities already, but there are still lots of things we can do like a powerful investment in renewable energy sources.
"So even strange bedfellows like the Pentagon are welcome. This may launch a debate in Washington that could have an impact on the administration."