Nuclear Winter

Nuclear winter is the climate catastrophe that Nuclear War — a Scenario devotes its final act to — the “new horror” the Earth plunges into after the warheads stop falling. Kyle’s notes trace its origin: the concept “first caught the world’s attention in October 1983,” when Parade magazine put a darkened Earth on its cover and ran a “special report” by Carl Sagan asking, “Would nuclear war be the end of the world?” Sagan’s answer was that the immediate billion-plus deaths in an “exchange” would be exceeded by the long-term consequences, which he, his former students James B. Pollack and O. Brian Toon, and meteorologists Thomas P. Ackerman and Richard P. Turco laid out two months later in Science.

The mechanism, as the book records it, is that soot and smoke from burning cities block the sun — the original 1983 models predicted the sun’s warming rays would drop by roughly 70 percent. The horror is its duration: “Our first models said nuclear winter would last about one year,” Toon explains, but “new data suggests the Earth’s recovery time would be more like ten years.” In the book’s chain of consequences, those who survive blast, fire, radiation, and cold then starve as transportation, fuel, and food distribution collapse — feeding the 2022 Nature Food conclusion that “more than 5 billion could die” from a U.S.–Russia nuclear war.

Context: “Nuclear winter” is the hypothesized severe global cooling that would follow a large-scale nuclear war, caused by firestorm soot lofted into the stratosphere blocking sunlight. The term and the foundational modeling are associated with the 1983 “TTAPS” study (Turco, Toon, Ackerman, Pollack, Sagan).

Where this appears

• Nuclear War — a Scenario — the book’s final act; traces the concept to Carl Sagan’s 1983 Parade/Science work and the ~70% sunlight reduction and ~10-year recovery estimates.