The “cloud ships” are favoured among a series of schemes aimed at altering the climate which have been weighed up by a leading think-tank.
The project, which is being worked on by rival US and UK scientists, would see 1,900 wind-powered ships ply the oceans sucking up seawater and spraying minuscule droplets of it out through tall funnels to create large white clouds.
These clouds, it is predicted, would reflect around one or two per cent of the sunlight that would otherwise warm the ocean, thereby cancelling out the greenhouse effect caused by Carbon Dioxide emissions.
The unmanned ships would be directed by satellite to areas with the best conditions for increasing cloud cover, mainly in the Pacific and far enough away from land so as not to affect normal rainfall patterns.
Other ideas, such as sending mirrors into space by rocket to deflect the sun’s rays, and scattering iron powder into the seas to boost CO2-absorbing plankton, have been dismissed as unfeasible or too expensive.
According to The Times, The Royal Society is expected to announce that the decade-old cloud ship plan is one of the most promising.
The Copenhagen Consensus Centre, which advises governments on how to spend aid money, examined the various plans and found the cloud ships to be the most cost-effective.
They would cost $9 billion (£5.3 billion) to test and launch within 25 years, compared to the $250 billion that the world’s leading nations are considering spending each year to cut CO2 emissions, and the $395 trillion it would cost to launch mirrors into space.
At present, British and American teams are seeking funding to launch sea trials. The US team has been boosted by a donation of several hundred thousand dollars by The Carnegie Institute, while the British team, led by John Latham, an atmospheric physicist at the University of Manchester, and Stephen Salter, an engineer at the University of Edinburgh, is working with a Finnish shipping company, Meriaura.
Bjorn Lomborg, director of the Copenhagen think-tank, is hosting a conference in Washington DC next month at which a panel of Nobel laureates will vote on the most cost-effective solution.
He believes the schemes could prove that there are better ways of addressing climate change than simply reducing CO2 emissions.
“The space sunshade is really just science fiction but cloud whitening ships deserve serious scrutiny,” he told The Times.
“We need to have a debate about all of the options, not just the politically correct one of reducing CO2.”
Another scheme considered by the Copenhagen Consensus Centre is one to mimic the effects of volcanic eruptions in shielding the sun’s rays with a chemical haze and creating a global cooling effect that can last for over a year.
The eruption of Mount Pinatubo in the Philippines in 1991 sent billions of tonnes of sulphur dioxide and other particles into the atmosphere which reduced global average temperature by about 0.5C. The eruption of Mount Tambora in Indonesia in 1815 saw 1816 become known as the year without summer.
Scientists have proposed various ways of emitting such particles into the atmosphere, including using squadrons of air tanker potentially based in the Arctic to protect the polar ice cap.