As Temperatures Keep Rising, Geoengineering Gets a Closer Look

As Temperatures Keep Rising, 'Plan B' Gets a Harder Look 2

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.

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 could dry out equatorial regions, accelerate sea-level rise, trigger wars, and sidestep the need to confront problems of fossil fuels beyond the simple issue of the earth's average temperature.

But now, after another year of