The four men are fond of using the word "urgent" in arguing for zero nukes. They worry less about a cold-war nuclear missile exchange, and more about jihadists seizing fissile material from, say, an unstable Pakistan, which has of late continued to produce more highly enriched uranium than it needs. Or a possible Middle East nuclear race by Egypt, Syria, or Saudi Arabia in the wake of a bomb made by the Shiite government in Iran. (This is to say nothing of what Israel's reaction might be.)
Yet Nunn and others say the dangers also encompass the possibility of human errors and mistakes by the traditional nuclear powers. US and Russian missiles, for instance, remain on a five-minute "quick launch" timetable, which Nunn calls a situation "bordering on insanity." Plus, as nations turn more to nuclear power as an answer to global energy needs, there will be an exponential increase in the reprocessing of plutonium or uranium, which can be used in making a bomb.
The post-cold-war era has brought the expansion of a global middle class and the comforts of Starbucks, iPods, Facebook, and nonstop sports, weather, and food channels. But the legacy of 20th-century nuclear science hasn't ended, the four say, even if it's often ignored or forgotten.