J. Geophys. Res. 112, D13107, (2007).

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Smoke generated by even a 'small' nuclear war would provoke deadly and widespread climatic disruption that would cause far greater mortality than the bombs themselves, finds a new study. Sudden and lasting cooling from the smoke blocking the sunlight would devastate agriculture worldwide for years and cause famine on a scale unprecedented in human history.

Alan Robock and colleagues at Rutgers University, New Jersey, ran two simulations, using a new global climate model that reaches up to the top of the mesosphere, approximately 80 km above the Earth's surface. One simulation assumed a war that unleashed some 20,000 weapons, equivalent to current Russian and US arsenals. The second assumed a war using one-third of those weapons.

All-out war would result in a true 'nuclear winter', says Robock. Soot would persist in the atmosphere for over a decade, resulting in average global cooling of as much as −7 °C, and would halve rainfall, leading to global famine. In the 'limited' war, temperature and rainfall reductions would be half as severe, but would last equally as long. The study is the first to use this type of model, including the ocean and atmosphere up to 80 km, to simulate the effects of nuclear warfare on the climate.