To this day physicists coincided with the consequences of the nuclear war: The temperature of the Earth would decrease and we would have to suffer the so-called nuclear winter. The cause of all this would be the clouds generated by atomic explosions (which would prevent sunlight from reaching the earth's surface) by dust introduced into the atmosphere.
Several physicists from the US Academy of Sciences propose a new panorama. They consider that in principle an instantaneous warming of the planet could occur. In the atmosphere, huge amounts of water vapor would be injected and the resulting cloud layer would return to the surface the infrared radiations (heat) that the earth reflects into space.
That is, a phenomenon known as a greenhouse effect would occur. The duration of the warming would depend on the duration of the clouds.