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Global warming can be halted by plumbing a gigantic array of pipes into the depths of the oceans, according to two of the world’s leading environ-mental scientists.

Pipes measuring up to 650ft (200m) long and 33ft in diameter should be installed and used to pump nutrient-rich water up to the surface to encourage plankton blooms, they say.

The plankton growth would then take carbon dioxide out of the atmosphere and encourage cloud formation that together would, they believe, cool the world and save it from global warming.

James Lovelock, the originator of the Gaia theory, and Chris Rapley, director of the Science Museum and a former head of the British Antarctic Survey (BAS), put forward the proposal in a letter to the scientific journal Nature. The two professors hoped that their proposal would encourage other scientists to concentrate on establishing novel techniques to halt global warming instead of writing off geoengineering as an impossible solution. But the idea ran into controversy at once, with one scientist branding it “a waste of time” and others expressing doubts about its effectiveness.

Under the proposal, hundreds of thousands of pipes, placed strategically in the seas, would be fitted with a buoyant collar to keep one end at the surface, where they would rise and fall with the waves. Each time they bobbed downwards several tonnes of water from several hundred feet beneath the waves would spill out at surface level. A valve would prevent water flowing back in at the top and would ensure that all water in the pipe came from the deep.

Extra nutrients at the surface would encourage blooms of microscopic plantlife, the professors suggested. These plants would extract carbon from the water, which would cause the water to absorb more carbon dioxide from the atmosphere.

A proportion of the plantlife would, when it died, sink to the seabed, where the carbon would be trapped and be unable to cause climate change.

Simultaneously, the blooms would emit dimethyl sulphide into the atmosphere, where it would play a role in cloud formation. Increased cloud cover is thought to reflect more of the Sun’s heat away from the Earth’s surface. The system would mimic natural upwellings that bring essential nutrients to the surface for plankton to consume.

In their letter the scientists described the proposal as an “emergency treatment”. They accepted that it might fail but said that it needed to be considered because of the dangers of man-made global warming. “We need a fundamental cure for the pathology of global heating,” they said.

Putting hundreds of thousands of pipes in the seas would create the potential to remove 500 gigatonnes of carbon dioxide from the atmosphere, they suggested. Professor Lovelock said he feared that political Kyoto-type solutions were too late to solve global warming. Instead, he envisaged tens of thousands of pipes over a distance of about 100 miles (160km) in the Gulf of Mexico, where an added benefit would be to damp down hurricane activity because cooler water would be brought to the surface.

Other scientists welcomed the proposal as thought-provoking but doubted that it would work.Corinne Le Quéré, who led research this year which showed that oceans were losing the capacity to soak up carbon dioxide, was scathing and feared that if pipes were deployed around the world’s oceans they could exacerbate, rather than cure, the warming trend.

“This idea is a complete waste of time,” said Dr Le Quéré, a researcher at the University of East Anglia (UEA) and the BAS. “It doesn’t make sense. There is absolutely no evidence that geoengineering options work or even go in the right direction. I’m astonished that they published this. Before any geoengineering is put to work a massive amount of research is needed – research which will take 20 to 30 years.”

Sir Brian Hoskins, Professor of Meteorology at the University of Reading, said there was “a strong scientific basis” for the scheme and agreed that “the current global political inaction on the climate issue is very serious”. But he was convinced that too little of the planet’s climate system was understood to make the effects predictable.

Andrew Watson, a professor who used to work with Professor Lovelock and is now at UEA, said: “I agree with Lovelock and Rapley that the stakes are so high that we must think creatively and take action, but I’m not sure this particular idea is the one I would start with.”

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