Several specialists suggested that storing carbon dioxide (CO2), the principal greenhouse gas, was not only technically feasible but also financially imperative, given the cost of tackling climate shift.

Their focus is on power stations that burn oil, gas and coal to generate electricity.

The CO2 would be captured in the plant's pipes as the fossil fuel is burned, then pumped out, sometimes over hundreds of kilometers (miles), to underground sedimentary basins and stored.

It would not be the miracle cure to global warming.

However, it would be a relatively cheap way of easing a dangerous further rise in carbon emissions in the next few decades, especially from China, which has a huge number of coal-fired power stations en route.

"This technology may be capable of supplying significant amounts of low-emission electricity within one or two decades," Jon Gibbins, of Imperial College London, said in a study prepared for the conference.

Environmentalists say the answer to global warming is to slash emissions themselves and swiftly wean the world's economy off dirty fossils and onto clean, renewable sources and hydrogen.

But there are also green pragmatists who reluctantly view carbon storage as a possible intermediate option, especially if it means that rich countries do not have to turn to nuclear power to curb their CO2 emissions.

The conference, being held in the southwestern English city of Exeter, was called by British Prime Minister Tony Blair, who has vowed to make global warming a priority of his presidency of the Group of Eight (G8) countries this year.

More than 100 scientists from 30 countries were invited to the meeting, with the goal of providing a snapshot of expert opinion to guide politicians.

They were to issue a document at the conference's close that would summarise the present state of knowledge, but not offer recommendations for action.

It is the biggest scientific forum 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 C (2.5 F) and 5.8 C (10.4) compared to

Mean global sea levels would rise by between nine and 88 centimetres (four and 35 inches).

The predicted consequences ranged from additional stress on water and food supplies in hot tropical countries to prolonged droughts and floods, violent storms, shrinkage of the polar ice caps and the meltdown of alpine glaciers.

These estimates depend on how much CO2 will be in the atmosphere by the end of the century.

The lower and upper ends of the IPCC's estimates are based on 540 parts of CO2 per million (ppm) and 970 ppm. In 1750, the benchmark for pre-industrialisation, concentrations were 280ppm.

Today, levels are about a third over the 1750 level. The world's average temperature rose by 0.6 C (1.08 F) from 1900-1990 alone.

The CO2 is now rising quickly, disgorged in particular by China and India and the United States, which accounts by itself for almost a quarter of greenhouse-gas pollution.

Stephen Schneider, a professor at Stanford University in California, said carbon pollution would inevitably race ahead in the coming years.

"I would be very surprised if the current growth rate of CO2 is not maintained for at least another two decades, no matter what policies are implemented," he said.

"I'll be very pleased, looking back, wherever I am looking back from, if in 100 years we are able to keep it to under a doubling of CO2. That will be an effort."

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