A nuclear holocaust, also known as a nuclear apocalypse, nuclear annihilation, nuclear armageddon, or atomic holocaust, is a theoretical scenario where the mass detonation of nuclear weapons causes widespread destruction and radioactive fallout, with global consequences. Such a scenario envisages large parts of the Earth becoming uninhabitable due to the effects of nuclear warfare, potentially causing the collapse of civilization, the extinction of humanity, or the termination of most biological life on Earth.
Besides the immediate destruction of cities by nuclear blasts, the potential aftermath of a nuclear war could involve firestorms, a nuclear winter, widespread radiation sickness from fallout, and/or the temporary (if not permanent) loss of much modern technology due to electromagnetic pulses. Some scientists, such as Alan Robock, have speculated that a thermonuclear war could result in the end of modern civilization on Earth, in part due to a long-lasting nuclear winter. In one model, the average temperature of Earth following a full thermonuclear war falls for several years by 7 to 8 °C (13 to 15 degrees Fahrenheit) on average.