But it's nothing that a few rich countries could not do. The US is spending more on its wars of choice, alone.
Whitening clouds might be cheaper, still. Here's a fun piece of a Scientific American article on geoengineering:
Geoengineering: How to Cool Earth--At a Price: Scientific American
In Salter's concept, turbines spun by water moving past the ship would generate the electricity to keep the cylinders spinning and also to spray seawater out the stacks in 0.8-micron droplets. Salter and Latham estimate that 1,500 ships, each spraying eight gallons a second--and each costing $2 million, for a total of $3 billion--could offset the global warming caused by a doubling of CO2. Half the job could be done, according to modeling results from the Met Office Hadley Center for Climate Prediction and Research in Exeter, England, by deploying ships over just 4 percent of the ocean. Still, no one has modeled how evenly the cooling would spread around the planet. "You could end up with a polka-dotted world, where there are really cold places and really hot places," Battisti says. Another concern is drought downwind of the spray vessels; clouds made of many small droplets last longer, which is desirable in a sunshade, but they also produce less rain. Finally, just how much brighter the new clouds would be is not known. Existing climate models overestimate the effect: according to them, the aerosols in the atmosphere right now should be canceling global warming, which is manifestly not happening. Rasch has thus started modeling Latham's idea. "This is one of the parts of climate that we understand most poorly," he says. Still, as geoengineering schemes go, spraying seawater into the air from wind-powered vessels sounds pretty benign. If anything went wrong, Latham says, you could shut off the spray within days or, at most, a few weeks--whereas sulfuric acid in the stratosphere would stay aloft for years. "It's definitely worth looking into," Wigley says. But only a field test could answer some of the questions about the idea--and so far the only support Latham has received has been from the Discovery Channel. In need of good visuals for a documentary series on geoengineering, television producers funded the construction of a small Flettner ship.
Still, no one has modeled how evenly the cooling would spread around the planet. "You could end up with a polka-dotted world, where there are really cold places and really hot places," Battisti says. Another concern is drought downwind of the spray vessels; clouds made of many small droplets last longer, which is desirable in a sunshade, but they also produce less rain.
Finally, just how much brighter the new clouds would be is not known. Existing climate models overestimate the effect: according to them, the aerosols in the atmosphere right now should be canceling global warming, which is manifestly not happening. Rasch has thus started modeling Latham's idea. "This is one of the parts of climate that we understand most poorly," he says.
Still, as geoengineering schemes go, spraying seawater into the air from wind-powered vessels sounds pretty benign. If anything went wrong, Latham says, you could shut off the spray within days or, at most, a few weeks--whereas sulfuric acid in the stratosphere would stay aloft for years. "It's definitely worth looking into," Wigley says. But only a field test could answer some of the questions about the idea--and so far the only support Latham has received has been from the Discovery Channel. In need of good visuals for a documentary series on geoengineering, television producers funded the construction of a small Flettner ship.
