An EMP (electromagnetic pulse) attack could permanently disable the electrical systems that run nearly all civilian and military infrastructures. If a large nuclear device exploded high in the atmosphere above the United States it would cause a catastrophe. A similar disaster could result from space weather, according to an article in National Geographic.
A solar storm begins with hot gas from the sun hitting the earth’s atmosphere, causing an electromagnetic catastrophe. A few weeks ago, the world experienced the largest solar storm since 2007; it caused radio communications problems and a disruption of civil aviation. The current 11-year cycle of solar storm is expected to hit in 2013; since 2000, the world has become even more dependent on global positioning systems for navigation and cell phone networks.