Great post on Velikovsky and Venus via Louis Hissink's Crazy World: Al Gore and Venus Envy.
Steven Milloy of the Junkscience site has just posted an interesting development - Al Gore has publicly stated what drive's his, and therefore Jim Hansen's, belief that CO2 is a dangerous greenhouse gas - Venus.
Jim Hansen's PhD was on the atmosphere of Venus and it is from this work that his belief in CO2 being a significant greenhouse gas is based.
The theory is wrong as was Carl Sagan who postulated that Venus was hot because of a runaway greenhouse mechanism.
This raises the ghost of Velikovsky for it was Velikovsky who initially proposed that Venus would be hot because of it's youthfulness based on historical evidence from many sources.
Mainstream science believed Venus was an earth-like arcadia, our sister planet! As Sagan could not admit that Venus was a young planet, he therefore had to come up with an ad hoc explanation to make this new discovery fit the "standard model", hence the runaway greenhouse effect.