Heat is not temperature - it is possible for hot objects to have a small amount of heat and vice versa. It just depends on what the object is made of.
Heat and Temperature
Heat is measured in calories (joules in the SI system), temperature in degrees Kelvin.
For each type of material, there is a constant - called Specific Heat - that relates the amount of heat to the temperature.
When a substance changes phase (solid to liquid, liquid to gas, and the reverse of each), heat is absorbed (or released) with very little change in temperature. This is termed "Latent heat of ..." and is sometimes referred to as enthalpy.
As a result, a substance like water has 6 different "Specific Heat" and "Latent Heat" values
|Ice||Solid||Specific Heat of ice|
|Melting||Solid to liquid phase transition||Latent heat of fusion (melting)|
|Water||Liquid||Specific Heat of water|
|Evaporation||Liquid to vapor phase transition||Latent heat of vaporization (evaporation)|
|Vapor||Gas||There is no constant for this - steam tables are used instead|
|Sublimation||Solid to vapor phase transition||Latent heat of sublimation / enthalpy of sublimation|
How Heat Moves
Physics books generally cover 3 ways that heat moves
|Conduction||When a metal spoon is placed in boiling water the handle tends to get hot. In this case, heat flows through the metal by conduction. If you use a wooden spoon, the handle stays cool. This indicates that metal is a better conductor of heat than wood.|
|Convection||Basically, this means that hot things rise and cold things sink.|
|Radiation||Heat can travel as Infrared (IR) radiation -
the slowest of all the heat transfer methods.
This is how heat from the sun reaches the Earth, and how the Earth releases the same heat, plus a little more (from the liquid core), back into space.
In the real world, these methods are also important
|Phase change||When you boil water, the temperature does not change. It does not matter how much more heat you add, the temperature stays the same as the water converts to steam. When a cloud forms, the water vapor looses heat.|
|Transport||In the old days, some people would heat rocks in a fire and then
place the rocks in a pot to cook the food. Today, we heat water
in a tank and transport it (via pipes) to the shower.
The Jet Stream, weather fronts, the Gulf Stream, and the like move tremendous amounts of heat from one area to another.
|Chemical Change||A battery stores energy via chemical change. Leaves convert energy (Sun light) into sugar.|
|Mixing||Stirring a pot will keep the bottom from burning. Physically mixing fluids of different temperatures moves heat faster than simple convection.|
Consider a hollow metal tube with both ends sealed. Inside the tube are a few drops of some liquid. As heat is applied to one end of the tube, the liquid vaporizes. At the other (cool) end, heat is loss and the vapor condenses back into the liquid phase. In the simplest configuration, the hot end is placed below the cold end so that gravity will pull the liquid back down. Other configurations exist.
Depending on the working temperatures, water, alcohol, freon, sodium, and many other materials can be used as working fluids. The only requirement is that the fluid must be liquid at the cool end and vapor at the other.
Most laptop computers contain heat pipes because there is not enough space for air to blow over the components. (My laptop has 2 - one for the processor and another for the video chip.)
Atmospheric Heat Pipes
The fact that air at the surface is usually warmer than the air above it helps - but it is not always necessary.
At some point, the expansion cools the rising air mass to the point where water begins to condense (forming clouds). Since the energy released is equal to the heat of vaporization, heat has been moved from the surface of the planet to the top of the clouds. At this point, the clouds act like mirrors reflecting the heat out into space.
Note - if the heat was released inside the cloud, it would simply be reabsorbed by the surrounding water droplets causing them to return to the vapor state. Therefore, the vapor *effectively* condenses only at the top of the cloud.
To complete the cycle, the condensed water returns as rain (or snow).
Even though there is no confining tube, I have described this cycle as an Atmospheric Heat Pipe because of the obvious similarities. These heat pipes are not the only way that the Earth cools itself - but they are the most efficient.
The model described here provides one mechanism for heat to move around the additional CO2.
Think of it this way
The Atmospheric Heat Pipe model presented in this page provides a very efficient mechanism to bypass this problem.
Of course, wind, weather fronts, and storms greatly complicate this model. My point was simply to show that simple evaporation followed, by cloud formation, effectively pokes a hole in the insulating atmospheric blanket so that heat can escape. As a result, if additional CO2 makes this blanket more efficient at holding heat, that will have almost no effect because the water driven heat pipe (phase change assisted heat transfer) will provide the necessary negative feedback.
One prediction of this model is that adding CO2 to the atmosphere will actually increase the amount of rainfall.
Note - Many Global Warming predictions include more storms AND expanding deserts - talk about covering ALL the bases.
The IPCC position
Please, don't just read the few quotes I've included below - read the entire section. It is painfully obvious that none of the models are very good ... and clouds are almost ignored.
22.214.171.124 Cloud-radiative feedback processes
126.96.36.199 Representation of cloud processes in models
Note - This section has a graph showing which models consider clouds as positive or negative feedback mechanisms.
The Atmospheric Heat Pipe I've presented above provides a major negative feedback mechanism that works to reverse any possible effects from increased CO2 - however, some climate models actually consider the feedback to be positive.
Note - Positive feedbacks will make a little heating get even hotter and negative feedbacks tend to make temperature changes very difficult.
I don't believe that there is enough evidence to believe that Venus is hot because its atmosphere is mostly CO2 - but those arguments will be discussed elsewhere. In the meantime, consider this