Add solar storms to the disaster risk list. These high-energy bursts can interact with the earth's magnetic field, creating geomagnetic storms that could bring sudden, extended and widespread power and telecommunications outages over the next few years. The next peak in the 11-year cycle of solar disruptions arrives in 2012.

"We've been lucky, because the kinds of storms we've had in recent decades have been relatively low-intensity compared to those in the historical record," says Sten Odenwald, an astronomer at NASA's Goddard Space Flight Center. Odenwald points out that society's growing dependence on technology–especially electricity grids–would exacerbate the impact of a really big storm.

The largest one on record, the Carrington Event in 1859, shut down most of the U.S. telegraph system. Another severe storm in 1921 disrupted railroad signaling and switching, sparked station fires in the northeastern U.S. and damaged Europe's telegraph and telephone lines. Canada's Hydro-Qu?bec power grid collapsed within 90 seconds after a storm began in 1989, leaving millions without electricity for up to nine hours.