Scientific American: Mimicking volcanoes by throwing particles high into the sky. Maintaining a floating armada of mirrors in space. Burning plant and other organic waste to make charcoal and burying it–or burning it as fuel and burying the CO2 emissions. Even replanting trees. All have been mooted as potential methods of “geoengineering”–“deliberate large-scale manipulation of the planetary environment,” as the U.K.’s Royal Society puts it. The goal, of course, is to cool the planet by remove …