"Nuclear winter" was one, among many, of the things hysterically screamed about by "Dr." Helen Caldicott and Physicians for Social Resposibility to show what an evil bad man Reagan was for wanting to put more Pershing 2s in West Germany and build neutron bombs. Caldicott never could get her story straight. First she claimed there would be a "nuclear winter". Then she said a thermonuclear war would result in a mega-"global warming" with loss of ozone causing sunlight to be magnified to the point of danger. Huh? Well, now you know the history of the same Physicians for Social Responsibility seeking bans on handguns and semi-auto firearms.
The fact is, several nuclear weapons were detonated above ground from 1950 to 1962. The fallout swept across Nevada and Utah and, at one point, was tracked clear to upstate New York where it allegedly entered the milk supply via grazing cattle. At one test, coal was piled under the shot tower to make the fallout "dirty" and, allegedly, easier to track. The "Sedan" shot, a test of the Project Plowshare song-and-dance scooped out plenty of fallout, though the AEC claimed it did not (see "Sedan Crater".) From Upshot-Knothole to Buster-Jangle, these atmospheric nuclear tests proved that fallout, while deadly, is not the all-killing power everyone thought it was. Though they will never admit it, one of the reasons behind some of those tests was to determine if a nuclear war was survivable. (Indeed, one test was done to try out different concepts of shelters for Civil Defense and what would happen to certain types of houses and cars.) Of course, these tests were individual tests and not a series of simultaneous detonations. But wind patterns are what they are and the deadiest fallout deteriorates in two to three weeks. Now, a biological attack of epic proportions by an unknown virus or bacteria could indeed be the whimper and not the bang by which mankind exits stage left and leaves earth to the next stage of evolutionary progress by some other species. Is man that dumb? Probably. We see what man did with unlocking the secret of the atom. What will he do with the secrets of DNA? Smallpox alone is bad enough to kill millions, especially now with all these Luddites who fear the vaccine more than the disease. (Geez, they never ASKED us in army basic training if we wanted the smallpox vaccination. They just said, "Hold sill recruit! Geez, I'm sill alive! I was too scared of the drill sergeants to let a couple little pin pricks make me sick!)