As Temperatures Keep Rising, Geoengineering Gets a Closer Look

U.S. National Oceanic and Atmospheric Administration

Phytoplankton, seen here under a microscope, are found in the upper levels of the world's oceans. One possible tactic for artificially cooling the earth involves spreading iron sulfate in the sea to feed the phytoplankton, which absorb carbon dioxide.
January 28, 2013 Premium content for subscribers. Subscribe Today

For all the fears and controversy about a warming planet, scientists have settled on one simple fact: It would be pretty cheap and easy to cool it back down again.

The potential side effects, however, are serious. Various tactics for blocking the sun...

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