Hahaha, it didn't appear first time!
If hot air rises, why is there snow on the tops of mountains?
Several reasons. Mainly due to air density. The lower down the greater the density. The greater the density the more often molecules collide and the heat transferance between these colliding molecules is what we feel as heat.
The higher the altitude the less dense the atmostphere is, therefore the frequency with which heat is created by clashing molecules is rarer. Any 2 given molecules could be miles apart, although they are hot and carry a large amount fo energy, it is the colliding of these molecules that creates heat.
I think, by definition, that temperature is just the measure of molecular activity. The higher the temp, the higher the molecular activity, or at least their speeds are higher anyway.
Or something like that. :?
I have edited to make me more correct. I was leaving work/school so didn't have time to give a decent explanation, and ensure my info was at least partially right!
