Nuclear summer
A Nuclear summer is a hypothetical scenario resulting from a nuclear war that would follow a nuclear winter. In this scenario, the amount of H2O in the stratosphere would increase, causing greenhouse warming of the surface. The nuclear detonations would also produce oxides of nitrogen (NxO) that would then deplete the ozone layer around the Earth. This layer screens out UV-B radiation from the Sun, which causes genetic damage to life forms on the surface. The absorption of O3 also results in a heating of the stratosphere, which results in a further contribution to greenhouse heating.
Other more simplistic versions of the hypothesis exist: that Nuclear winter might give way to a nuclear summer. The high temperatures of the nuclear fireballs could destroy the ozone gas of the middle stratosphere [1].