4. Nuclear War

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Even though the long-running cold war ended between the United States and the Soviet Union in 1989, the threat of nuclear war is as real today as ever. Emerging  potential threats such as North Korea and Iran are believed to be developing the capability to launch nuclear-tipped ballistic missiles which can travel for thousands of miles to reach their targets. A limited nuclear exchange would probably be survivable by the majority of the world’s population but an all-out nuclear holocaust would probably result in “nuclear winter,” a scenario not unlike the aftermath of a major asteroid impact.