File this one under "How to spend that spare $9 Billion you have laying around not doing nothing".
From Telegraph.co.uk: ""Cloud Ship" Scheme to Deflect the Sun's Rays is Favourite to Cut Global Warming (8/7/09)
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.
[...]
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.
