We as a species are currently dumping massive amounts of carbon into the upper atmosphere.  Average temperatures around the world are rising at an alarming rate, evidently at least in part as a consequence of this dumping.  No movement is in prospect that would stop the dumping, or even reduce it substantially.  So, what to do?  Some scientists and engineers want to remake the rest of the earth’s climate to accommodate our carbon dumping habit.  How could this be done?  There are several possible methods. 

We could shoot sulphur dioxide into the upper atmosphere.  That would be remarkably affordable- for as little as a billion dollars, it could end global warming.  The drawback is that eventually sulphur would rain down from the sky, and if we stopped shooting new sulphur dioxide up there global temperatures would increase dramatically in a very short period.  Also it would cause severe droughts throughout central Africa, a region which has not exactly been among the big winners of industrialization to start with, so that seems unfair. 

Also we could dump iron powder in the Antarctic Ocean, causing a huge plankton colony to bloom and suck carbon dioxide out of the atmosphere.  We’d have to be a bit careful about that- half a supertanker’s worth of iron powder could feed a big enough plankton bloom to trigger a new Ice Age.  And when plankton dies, it releases methane, which is a much more effective greenhouse gas than carbon dioxide. 

There are also people who would like to block sunlight by shooting millions of clay discs at the Lagrange point between the earth and sun.  These skeets might well reduce average temperatures on the earth, but they could also stop the formation of ozone in the atmosphere.  And without an ozone layer, life as we know it could not exist on the surface of the earth.  So that’s a little bit on the risky side too.  So it seems like reducing carbon emissions might be worthwhile after all. 

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