Space weather is not all bad. After all, the charged particles streaming out from the sun that cause geomagnetic disturbances on and around our planet also produce the lovely aurorae near Earth's poles—and sometimes at much lower latitudes.

But when the sun really acts up, spewing out heaps of charged particles in a burst called a coronal mass ejection, space weather can get a bit more menacing—and future storms could be even worse than the ones we’ve experienced. Solar storms can damage power grids, fry communications satellites and disrupt aircraft electronics. A few oft-cited historical examples: a 1989 solar storm caused billions of dollars in damages in Quebec and triggered a blackout affecting millions. An even bigger storm in 1859 rocked telegraph systems in the U.S. and abroad; the induced currents coursing through the wires were so strong that they ignited fires in telegraph offices. If something like that happened in today's vastly more wired world, country-size regions could lose power for months, according to a recent U.K. assessment; the damages could run into the trillions of dollars.

But what if the superstorm of 1859 isn't even as bad as it gets? The problem is not just that our technological world is vulnerable to stormy space weather, which it is, but also that we don't really know what kind of storms to expect, according to a commentary in the April 19 issue of Nature by Mike Hapgood of the Rutherford Appleton Laboratory in the U.K. (Scientific American is part of Nature Publishing Group.)

"In the long term, we still have little sense of what maximum space weather event we should prepare for," Hapgood notes. He adds that many power grids are now built so that their transformers can withstand an event the size of the 1989 Quebec storm. But sooner or later that level of preparedness will be insufficient: "Last year’s earthquake and tsunami in Japan show the dangers of preparing only for an event similar to that seen in recent decades." We already know that bigger storms happen on relatively short timescales—both the 1859 storm and a 1921 event were much more powerful than the 1989 flare-up.

Hapgood is certainly not the first to sound the alarm about the threat of solar superstorms. But his recommendations for how we could start grappling with the problem are surprisingly attainable, if a tad unsexy. Yes, utility operators must beef up power grids with more robust transformers and devices that block storm-induced currents, and space weather forecasters must find ways to better predict the timing and severity of incoming coronal mass ejections. But if we really want to learn what the worst-case scenario looks like, we could start small, by digitizing reams of data on past events. "Most historical data sets exist only on paper as charts or tables, sometimes handwritten," Hapgood notes. "These include ionospheric data going back 80 years and magnetic data going back 170 years." Bringing those records into the digital realm, where more people could access them, would boost researchers' understanding of what kinds of storms occur how often. Another approach: improving the physical models that simulate how the swirling plasma in a coronal mass ejection propagates through space, and how it affects Earth when it hits. "In this way," Hapgood writes, "extreme events can be simulated before they happen."

No matter how well we understand space weather—and at the moment we don't understand it very well—solar storms will always be a fact of life. In fact, Hapgood views them as "a generic environmental risk to society and the economy, in parallel with earthquakes, volcanoes and floods." Let's just hope we won't have to weather the solar-storm equivalent of a 100-year flood before society gets serious about preparing for the worst.