Tweaking The Clouds To Cool The Planet

A ship with “Flettner rotors” that spin about their vertical axis and act as sails. Seawater sprays from the tops to seed the clouds.

Remember the industrialist villain in “Superman III” (1983)? Ross Webster (Robert Vaughn)? Furious at Colombia’s refusal to do business with him, he decides to brew a storm over that country to destroy all its coffee crops.

Now, even climatologists have begun considering technological fixes to counter the effects of humanity’s continued climate intervention—by relentlessly spewing tons and tons of heat-trapping carbon dioxide into the air.

Earlier this year, the National Academy of Sciences convened a panel of experts who assessed two “geo-engineering” strategies to cool the planet.

One approach is to make the atmosphere more reflective, so that it retains less heat. Called “albedo modification,” these technologies seek to regulate the quantity of sunlight entering Earth by increasing its “albedo”—that is, the amount of sunlight it radiates back out into space.

One way to do that is “marine cloud brightening,” which involves shooting jets of briny seawater into the sky from giant nozzles, on board a fleet of roving robotic ships.

These vessels would be powered by the wind, but wouldn’t have sails. Instead, they’d be fitted with enormous cylinders, known as “Flettner rotors,” which would spin continuously, propelling them forward. They’d also serve as sprayers.

When the mist hits the air, the small salt grains in it would become new loci for water vapor to condense around, enabling the formation of clouds with more numerous, but smaller, water droplets.

Just as crushed ice provides more surfaces for light to reflect off—appearing brighter than a solid cube of ice—so do clouds packed with tiny droplets. They’re also whiter than they otherwise would be. Brighter clouds, in turn, offer more shade.

But this proposition is fraught with too many serious risks.

Another way to mitigate the effects of global warming is “carbon sequestration,” which would directly scrub the air of excess carbon dioxide. Klaus Lackner and Allen Wright at Columbia University’s Earth Institute are working on a project to build a Swiffer duster-like structure, which is a small-scale version of an “artificial tree.”

All plants and trees breathe in carbon dioxide during photosynthesis, and breathe out oxygen, in the process, cleaning the air. But these will remove much more of the greenhouse gas, and much faster. The team envisions creating “forests” of this synthetic foliage.

On a day, each unit will extract a ton of carbon out of the air, the equivalent of emissions produced by 36 vehicles. It can then be put to use in factories or stored away safely underground.

This method addresses the root cause of climate change, which is the high atmospheric concentration of carbon dioxide. Albedo modification, on the other hand, would only temporarily mask the heating effect of greenhouse gases.



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