Except that Venus' temperature is caused by ~92 atmosphere of pressure.

Derivation:
The adiabatic lapse rate = dT/dz = -Mg/R*(y-1)/y = ~7.82K/km (I was lazy and used 100% CO2 for this, also y = gamma) which isn't too far off from the ALR calculated from measurements using least squares = ~7.74K/km.

T(z) = Tsurface - ALR*z, by definition (~= 735 - 7.82z).
The barometric equation is P = Psurface*e^(-Mgz/RT).
Solving for z = -RT/Mg*ln(P/Psurface),
  and plugging into T(z), we get T(P) = Tsurface - (y-1)/y*Mg/R*RT/Mg*ln(Psurface/P)
  = T = Tsurface - (y-1)/y*T*ln(Psurface/P),
  rearranging, T(P)*(1+(y-1)/y*(ln(Psurface)-ln(P))) = Tsurface
  Thereforce T(P) = Tsurface/(1+(y-1)/y*(ln(Psurface)-ln(P)))

So the only things that cause the Greenhouse Effect (on Venus, water makes the calculation more complex for Earth) are specific heat capacity, and pressure. By the time CO2 reaches levels enough to affect the climate, we'd be dead from poisoning.

Yeah, I searched a bit more, and The Algonquin Wits would be from the Algonquin round table, which was from 1919-1929, so the Mussolini book is probably correct. This is going to bug me enough that since there's no clear answer on the internet I'll head to the library.

TO ANYONE COMING FROM A SEARCH ENGINE: my quote is probably incorrect, and I don't have a copy of The Algonquin Wits to look up the correct answer. Also, why are you looking up information on the internet, which was clearly created to spread vicious rumors and slander, half-truths, parroting stuff someone else said as verbatim, misattributes, and all other manner of general dishonesty.

There, I've served my penance.