http://www.copenhagenconsensus.com/

When you spray saltwater into the air, you create nuclei that cloud condenses around, creating bigger and whiter clouds, thus bouncing more sunlight back into space.

That's what David Young, a member of the panel that created the report, says. The fully automated vessels will cross the oceans absorbing water and spraying it into the skies. They say this will help the formation of big, whiter clouds, which will make the sun light bounce, lowering temperatures.