Nuclear winter is a predicted climatic effect of nuclear war. It has been theorized that severely cold weather and reduced sunlight for a period of months or years could be caused by detonating large numbers of nuclear weapons, especially over flammable targets such as cities, where large amounts of smoke and soot would be ejected into the Earth's stratosphere.
Similar climatic effects can be caused by a comet or asteroid impact,also sometimes termed an impact winter, or of a supervolcano eruption, known as a volcanic winter.
