A bullshit scenario concocted during the Cold War to scare the US into giving in to the Soviets.
It goes like this: the fires produced by the nuclear bombing of targets would inject large amounts of smoke into the atmosphere. The smoke would coalesce into a layer that would block sunlight from reaching Earth's surface. A massive drop in temperatures would result. Here's where the scare tactics kick in: the lack of sunlight would deprive plants of vital energy, causing an extinction event.
This sob story was busted in a 1986 paper called "Nuclear Winter Reappraised." However, the paper was ignored, and fear of nuclear winter continues to subsist.
The people who came up with "nuclear winter" were not objective scientists but partisan agitators. Their goal was to see the U.S. back down from the Cold War. The most prominent scientist, Carl Sagan, was an enthusiastic proponent of nuclear disarmenent.
A alternative theory to evolution for the origins of life. Intelligent Design is NOT grounded in religion. It does not name a specific entity as the "Intelligent Designer." Instead, it proposes that intelligence is a force in the universe, like gravity, and that its effects can be seen in the development of life on Earth. Unfortunately, the opponents of Intelligent Design have succeeded in convincing the government and public that the theory is religion in disguise and teaching it in public schools violates the seperation of church of state. This myth has been so ruthlessly propogated that any evidence disproving it is flagrantly ignored.
It doesn't matter whether Intelligent Design is correct or not. What does matter is that it is a true scientific theory and deserves to be taught as such, if only to break the monopoly evolution has on scientific theories for the origin of life.