Giant engineering schemes to reflect sunlight or suck carbon dioxide from the air could be the only way to save the Earth from runaway global warming, according to a group of leading scientists. But they say that these schemes could have their own catastrophic consequences, such as disrupting rainfall patterns, and should be deployed only as a last resort if attempts to reduce greenhouse gas emissions fail.

The Royal Society, a fellowship of 1,400 of the world’s most eminent scientists, published a report yesterday on the feasibility and possible dangers of technologies for cooling down the Earth, known as geoengineering. The ideas include artificial trees that draw CO2 from the air and mimicking volcanoes by spraying sulphate particles a few miles above the Earth to deflect the Sun’s rays. The most far-fetched would would be to launch trillions of small mirrors into space to act as a sunshield.

A far cheaper solution would be a fleet of 1,500 ships that would suck up seawater and spray it out of tall funnels to create sun-reflecting clouds. However, the report said that these clouds could disrupt rainfall patterns and result in mass starvation in countries dependent on the monsoon.

The panel of 12 scientists who produced the report concluded that all these approaches were theoretically possible and, despite the potential side-effects, should be explored with a view to holding trials.

They called for a 160 million annual global research fund to study geoengineering technologies and said that Britain should contribute 16 million a year, ten times the amount being spent now on such research.

Professor John Shepherd, who chaired the panel, said: “It is an unpalatable truth that unless we can succeed in greatly reducing carbon dioxide emissions we are heading for a very uncomfortable and challenging climate future, and geoengineering will be the only option left to limit further temperature increases."

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