Climate changes associated with nuclear war

Nuclear war, featuring explosion of half the world arsenal of nuclear weapons, would cause urban and forest fires that would inject 20-650 megatons of smoke into the atmosphere. The Northern Hemisphere optical depth would increase to between 0.5-14. All models indicate an increase in optical depths, a large net radiation gain in the smoke layer, and an antigreenhouse effect at the surface. Significant global cooling would proceed, transforming the global climate to a large degree toward that of an airless world. Persisting deficiencies in the models are identified, noting research areas which would improve the accuracies of the predictions.