Electromagnetic Threats Overview
Recent reports from NASA, NOAA, DoE, and DoD from 2008-2009 show that the effects of a 100 year solar storm is now considered to be roughly ten times larger than previously expected, making it possible for a one-year blackout in our time. The likelihood of a 100 year storm, given enough time, is 100% and would cause immediate economic loss of $1-2 trillion and require a 4-10 recovery.
Similarly, man-made EMP attacks are the most devastating of all cyber security threats and can create the highest economic damage for the least cost. As long as little is done to harden critical infrastructure against the threat, the likelihood is relatively high. The economic effects of a regional EMP attack, (either from a smaller nuclear weapon or an enhanced EMP weapon detonated 50-80 miles above the U.S. east coast) without considering the costs of repair, secondary effects within the region, or cascading effects outside of the region, have been shown to reach $790B. These concerns have been voiced by a unanimous consensus of the US Congressional Electromagnetic Pulse (EMP) Commission, the EMP report of the Congressional Research Service, and a Department of Defense report on the topic.
For a video presentation on both man made and natural EMP threats, see this link to NAT GEO's "Electronic Armageddon".
Fortunately, the same defenses can be used to protect against more targeted and local threats from directed energy weapons.