The ozone losses predicted in the study are much larger than losses estimated in previous «
nuclear winter» and «ultraviolet spring» scenario calculations following
nuclear conflicts -LSB-...] A 1985 National Research Council Report predicted a global
nuclear exchange involving thousands of megatons of explosions, rather than the 1.5 megatons
assumed in the PNAS study, would deplete only 17 percent of the Northern Hemisphere's stratospheric ozone, which would recover by half in three years.