http://www.astronomytoday.com/astronomy/venus.html states that the albedo of Venus is .76.

If I am understanding this correctly (I may not be), then the upper clouds of Venus reflect 76% of the light that falls on them.

I think you have just demonstrated that the temperature of Venus can not be due to solar heating even with the high CO2 content of it's atmosphere.

As is mentioned in the original post, Venus has a 90 times greater pressure than the earth does. When a gas is put under pressure, it heats up. At 90 times that of the Earth's pressure that would be about 1350 lbs per square inch (versus The Earth's 15 psi).

Also, Venus and Mars have no global dipole magnetic field. Some theories state that the lack of such a magnetic field accounts for Mars not having much atmosthere. The Solar wind has stripped it away. Earth's magnetic field protects our atmosphere from this fate.

Why does Venus have such a massive atmosphere if it has no such magnetic field? Venus is larger, and thus has more gravity than Mars, but after 4.5 billions years you would think that Venus proximity to the Sun (versus Mars) would strip away the atmosphere to a very large degree.

Maybe Venus' volcanoes are responsible for there still being an atmosphere, it's density, and the heat of the atmosphere. This would be due to the heat escaping the interior of Venus, and the compression of it's atmoshpere due to gases being added at a catostrophic rate.

However, (as is pointed out in the 1st article) the atmospheric pressure of Venus is 90 times that of the Earth. It's atmosphere has far more matter in it to hold heat, carbon dioxide regardless.

Also, Venus is much closer to the sun than the earth is. Because of the inverse square law Venus gets far more energy from the sun than the earth does.

The percentage of CO2 in the atmosphere of Venus is about 95%. On the Earth it is .038%.

Now, Mars also has an atmosphere of about 95% CO2, but an atmospheric pressue of about 1/100 of the Earth's. It is also much further than the Earth from the sun.

The conclusion is that the high temperature of Venus is due to it's proximity to the sun, and it's extremely large mass of atmosphere, not due to it being just CO2. If CO2 were the main reason for it's heat, then Mars would be far warmer than it is.