It's true, this blog hawks a lot of different apocalyptic scenarios. They help us get out of bed in the morning. Some of our doomsday worries are well-founded (rising global temperatures, say), while some are less worth obsessing about hourly (giant asteroids, supervolcanoes). But how should we rank this cataclysm-in-waiting?

It is midnight on 22 September 2012 and the skies above Manhattan are filled with a flickering curtain of colourful light. Few New Yorkers have seen the aurora this far south but their fascination is short-lived. Within a few seconds, electric bulbs dim and flicker, then become unusually bright for a fleeting moment. Then all the lights in the state go out. Within 90 seconds, the entire eastern half of the US is without power.

A year later and millions of Americans are dead and the nation's infrastructure lies in tatters. The World Bank declares America a developing nation. Europe, Scandinavia, China and Japan are also struggling to recover from the same fateful event—a violent storm, 150 million kilometres away on the surface of the sun.

It sounds ridiculous. Surely the sun couldn't create so profound a disaster on Earth. Yet an extraordinary report funded by NASA and issued by the US National Academy of Sciences (NAS) in January this year claims it could do just that.

That's how Michael Brooks dramatizes a recent NAS report about the possibility that the sun, during a period of intense activity, could shoot off a billion-ton high-energy plasma ball that thwaps Earth and wreaks havoc on our magnetic field. If that happened, the magnetic field could induce extremely strong currents in our power grids that would fry the copper wiring in the transformers. Something like this actually happened in Quebec in 1989—a geomagnetic storm left six million people without power for nine hours—but that was a relatively low-intensity space storm.

How likely is a massive one? Back in 1859, the Carrington event hit Earth—a huge solar flare that produced stunning auroras as far south as the Equator but also disrupted the world's telegraph networks and drove magnetometers haywire. Luckily, the world wasn't totally dependent on high-voltage electric grids back then. But we are today! And if, say, a severe weather event knocked out 300 key transformers in the United States within 90 seconds—as the usually cautious NAS concedes is wholly possible—well, then that'd be 130 million people without power, and it'd take forever to get those transformers back. (Most major utilities have just one crew on hand capable of replacing a melted transformer hub in a week or two. But 300? It'd take ages.)

Suffice to say, it's not fun to think what would happen to a developed country without electricity: good-bye medical care, good-bye reservoir pumps, good-bye supermarkets. Hope you've got ammo. The National Academy of Sciences pegs the economic impact of a "severe geomagnetic storm" at $2 trillion during the first year alone—with recovery taking anywhere from four to ten years. Ironically, developing countries, which are less dependent on modern high-voltage grids, would probably fare best. (Europe's intricate electric grid, by contrast, is absurdly vulnerable to failures—a breakdown in one sector tends to ripple quickly through the whole system.)

The good news is that if they had, say, 15 minutes fair warning, power companies could probably prepare their grids for a wacky magnetic event and avert disaster. And lo, NASA's Advanced Composition Explorer is orbiting between the sun and Earth and can detect solar winds and other odd particles flying our way. The not-so-good side is that the ACE is getting old and onboard detectors are getting sort of rickety. Also, a truly major coronal mass ejection like the Carrington event might send a plasma ball our way in less than 15 minutes time—not enough to prepare. Maybe we should, uh, replace that satellite.

Anyway, something to keep us up at night. (Armageddon, by the way, is most likely to hit around spring or fall of 2012—heightened solar activity year plus equinoxes.) One related, more sober aspect of this, though, is that even if you blithely ignore the doomsday talk, the world's still becoming increasingly reliant on GPS systems, which are critical for everything from oil-rig placement to light-aircraft navigation. And space weather, which is likely to ramp up over the next few years, could cause very frequent GPS failures. So even if you're not of an apocalyptic mindset, it's still worth figuring out how to deal with geomagnetic storms.