How bad would nuclear winter caused by a US-Russia nuclear exchange be?

Abstract

A nuclear exchange between the US and Russia would likely involve counterforce targeting, with attacks on each other’s nuclear forces, rather than countervalue targeting, which would involve attacks on cities and industry. Nuclear attacks on cities would likely produce much more smoke than attacks on missile silos and military bases because cities have much more flammable material. An estimated 13–67 Tg of smoke would be emitted into the atmosphere following a nuclear exchange between the US and Russia. This would lead to a decrease in global temperatures of 1.6–4.2 degrees Celsius and a decrease in global precipitation of 9.2–24%. The effects on agriculture would be substantial, leading to widespread crop failures and food shortages. An estimated 2.7–7.5 billion people would die from the resulting famine. – AI-generated abstract.