Campaigners have criticised plans for a sea trial of cloud-whitening technology, funded by Microsoft founder Bill Gates.
A US-based research body, Silver Lining, which has received $300,000 from Mr Gates, is developing machines to convert seawater into microscopic particles to be sprayed into clouds. Scientists believe this will increase the whiteness, or albedo, of clouds and increase their ability to reflect more sunlight back into space, reducing global warming.
The Gates-backed sea trial would be the largest known attempt to geoengineer the climate so far, reported to be conducted over an area of 10,000km2.
However, campaigners say such a large-scale trial is 'risky' and that a global ban on geoengineering experiments should be put in place until regulations governing the sector can be introduced.
'We knew Microsoft was developing cloud applications for computers but we didn’t expect this. Bill Gates and his cloud-wrenching cronies have no right to unilaterally change our seas and skies in this way,' said Jim Thomas from Canadian environmental campaigners, ETC Group.
In March, MPs from the Science and Technology Committee back such calls and said countries should not be allowed to take unilateral action on geoengineering without consulting the UN.
A major report on the subject by The Royal Society last year also warned of the unknown side-effects of cloud-whitening, including, changes to regional weather patterns and ocean currents.
However, the report said it had advantages over other forms of geoengineering because it could be stopped immediately, and within ten days nearly all of the salt paricles would rain or settle out of the atmosphere.
It could also be used over Arctic to reduce summer ice melt, the scientists said.
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