My position is that LightbulbSun and Anttech have offered no reason to believe that the detonation of ten nuclear missiles is sufficient to wipe out the human race, or even half of American/European civilisation.
Sure, with the exception of the Soviet doomsday bomb, which was never built, nothing that I have ever heard would suggest that ten nukes are sufficient to wipe us all out. In fact, there have been plenty of above ground detonations.
Number of above ground detonations:
Country / detonations / year / total yield
United States 216 1945-1962 153.8 mt
U.S.S.R. 214 1949-1962 281.6 mt
United Kingdom 21 1952-1958 10.8 mt
France 46 1960-1974 11.4 mt
P.R.C. 23 1964-1980 21.5 mt
South Africa 1 1979 0.003 mt
So there have been 521 above ground detonations with a combined yield of ~480 Megatons. However, many of those tests involved relatively low yields. The largest bomb ever detonated was the Tsar Bomb at 50 mt., and codenamed... Ivan.
However, I don't think anyone can provide evidence to suggest that limited nuclear war is possible. The only examples would be from WWII, and no one but us had the bomb. Also, a runaway escalation of events was always a hallmark of cold war scenarios.
It is also important to remember that air bursts do not create nearly the problem that a ground level burst would.