An uncut version of this article, with additional content that had to be removed from the print edition for space reasons, can be found here.

A thunderhead towers at knee level, throwing tiny lightning bolts at my shoes. I'm standing--rather, my avatar is standing--astride a giant map [SLurl] of the continental United States, and southern Illinois, at my feet, is evidently getting a good April shower.

The weather is nicer on the East Coast: I can see pillowy cumulus clouds floating over Boston and New York, a few virtual meters away. I turn around and look west toward Nevada. There isn't a raindrop in sight, of course; the region's eight-year drought is expected to go on indefinitely, thanks to global warming. But I notice something odd, and I walk over to investigate.