Scientists have discovered the first unequivocal link between man-made greenhouse gases and a dramatic heating of the Earth’s oceans.

The researchers - many of whom are funded by the US Government - have produced what they have described as a "stunning" correlation between a rise in ocean temperature over the past 40 years and pollution of the air with greenhouse gases.

In a study that destroys a central argument of global warming sceptics within the Bush Administration - that climate change could be a natural phenomenon - the scientists have produced the first clear evidence of man-made warming of the oceans.

The researchers say the dramatic findings should convince President Bush to drop his objections to the Kyoto treaty on climate change.

"This is perhaps the most compelling evidence yet that global warming is happening right now," said Tim Barnett, a marine physicist at the Scripps Institution of Oceanography in San Diego and a leading member of the team.

"We’ve got a serious problem ahead of us. The debate is no longer ‘is there a global warming signal’ the debate now is ‘what are we going to do about it? How are we going to meet the challenges that are ahead of us?’ " he added.

The findings are crucial because much of the evidence of a warmer world has until now focussed on air temperatures but it is the oceans that are the real driving force behind the Earth’s climate, and yet little was known about how they have responded to the rise in greenhouse gases.

"Over the past 40 years there has been considerable warming of the planetary system and approximately 90 per cent of that warming has gone directly into the oceans. So if you want to go and find out what’s causing it, that’s the place to look," Dr Barnett said.

"We did look. We defined a fingerprint if you wish of ocean warming. Each of the oceans warmed differently at different depths and constitutes a fingerprint which you can look for," Dr Barnett told the American Association for the Advancement of Science in Washington DC.

"We had several computer simulations, for instance one for natural variability - could the climate system just do this on its own? The answer was clearly no," he said.

"We looked at the possibility that solar changes or volcanic effects could have caused the warming - not a chance. What just absolutely nailed it was greenhouse warming," he added.

America produces a quarter of the world’s greenhouse gases yet under President Bush it is one of the few developed nations not to have signed up to the Kyoto treaty to limit emissions. The President’s advisers have argued that the science of global warming is full of uncertainties and that climate change might just be a natural phenomenon.