British Environment Secretary Margaret Beckett, speaking at the start of the three-day meeting of world climate scientists, said global warming was a problem to which all countries contributed and it needed an international response.

"A significant impact (on the world's climate system) is already inevitable," she said. "(...) No one country, not even one continent, can solve the problem by acting alone."

Beckett hailed the Kyoto Protocol, the UN's pact on carbon pollution, which takes life on February 16 after years of bitter negotiations and rejection by US President George W. Bush.

Bush declared after first taking office in 2001 that the deal was too expensive for the oil-dependent American economy, which by itself accounts for roughly a quarter of all global carbon pollution.

"Kyoto is very much a first step," said Beckett, who also lobbied for clean technology and encouragement for developing countries not to follow rich nations down the path of fossil-fuel pollution.

She admitted that it was "out of the question" for Washington to return to Kyoto, but "we would like to see America engaging very much more fully" in international cooperation on carbon pollution.

The Exeter conference, "Avoiding Dangerous Climate Change," gathers more than 100 scientists from 30 countries.

The forum has been called by Bush's closest political friend, British Prime Minister Tony Blair, who as president of the Group of Eight (G8) countries has been lobbying Washington to do more on tackling climate change.

It is the biggest scientific confab on greenhouse gases since the publication in 2001 of a report by the UN's top expert group, the Intergovernmental Panel on Climate Change (IPCC).

That report -- next to be updated in 2007 -- calculated that, by 2100, temperatures would rise by between 1.4 degrees Celsius (2.5 Fahrenheit) and 5.8 degrees Celsius (10.4) compared to 1990 levels.

More than three dozen papers are to be presented in Exeter, and they will be synthesised in a set of conference conclusions that will be submitted to the Group of Eight nations.

But there will not be any recommendations, such as setting a target for a maximum rise in temperature of emissions of carbon dioxide, said conference chairman Dennis Tirpak.

"Those are the tasks of politicians... they are to decide what is hot enough," he said.

The studies range from highly technical reports on improving computer models to predictions about the impact of climate change on crops, biodiversity and disease.

At the apocalyptic extreme is a risk assessment of a shutdown of the Gulf Stream, a current which originates in the tropical Western Atlantic and bathes the coastline of Western Europe.

If the stream were stopped, or even significantly slowed, by a rush of melting freshwater from the Greenland icesheet, Western Europe would plunge back into the Ice Age.

The Kyoto Protocol requires industrialised signatories to trim output of six greenhouse gases by a deadline of 2008-2012.

But scientists say this effort is puny compared to what is needed if we want to avert climate change that could be potentially catastrophic and long-lasting.

At best, without the United States, Kyoto will shave two or three points of the predicted 30-percent rise in global CO2 emissions between 1990 and 2010.

One problem is that even if pollution were slashed immediately, temperatures would continue to rise because of the gas which has already been spewed into the atmosphere.

"The inertia can carry the impacts, especially on sea level rise, for centuries, if not for millennia," IPCC chairman Rajendra Pachauri told the conference.

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