The temperature of Venus is 455 degrees because CO2 floats in the air. This is where is we are heading because we are drawing it out of the Earth, trapping it and increasing temperature.
The arithmetic of absorption of infrared radiation also works to decrease the linearity. Absorption of light follows a logarithmic curve (Figure 1) as the amount of absorbing substance increases. It is generally accepted that the concentration of carbon dioxide in the atmosphere is already high enough to absorb almost all the infrared radiation in the main carbon dioxide absorption bands over a distance of only a few km. Thus, even if the atmosphere were heavily laden with carbon dioxide, it would still only cause an incremental increase in the amount of infrared absorption over current levels. This means that a situation like Venus could not happen here. The atmosphere of Venus is 90 times thicker than Earth’s and is 96% carbon dioxide, making the atmospheric carbon dioxide concentration on Venus 300,000 times higher than on Earth. Even so, the high temperatures on Venus are only partially caused by carbon dioxide; a major contributor is the thick bank of clouds containing sulfuric acid . Although these clouds give Venus a high reflectivity in the visible region, the Galileo probe showed that the clouds appear black at infrared wavelengths of 2.3 microns due to strong infrared absorption . Thus, Venus’s high temperature might be entirely explainable by direct absorption of incident light, rather than by any greenhouse effect. The infrared absorption lines by carbon dioxide are also broadened by the high pressure on Venus , making any comparison with Earth invalid.
Not to mention the fact that Venus is a lot closer to that big yellow thing that Al Gore denies has any real effect on changing temperatures on Earth.