The cold war between the superpowers not only left the entire world cold in fear, but perhaps also cooled the Earth, say Russian researchers K Y Kondratyev and G A Nikolsky. Their theory is that the atmospheric nuclear tests of the early 1960s released into the stratosphere vast amounts of nitrogen oxides, which combined with sunlight, expedited ozone depletion. The oxides triggered off ozone-destroying reactions, thus using up a part of the sunlight that would otherwise cross the stratosphere and warm the surface of the Earth.