Nuclear winter is a hypothetical global climate conition that is predicted to be a possible outcome of a large-scale nuclear war. It is thought that severely cold weather can 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 injected into the Earth's stratosphere. The term has also been applied to one of the after-effects of a comet or asteroid impact, also sometimes termed an impact winter, or of a supervolcano eruption.