Question: why when you climb a mountain, you get closer to the sun but it gets colder?

David Pyle answered on 16 Mar 2011:

The atmosphere at sea level has a pressure (1 bar, or 1e5 Pa) due to the weight of the atmosphere above. As you climb upwards, the weight of the atmosphere above you falls, and pressure drops so that at, say, 5 km elevation the pressure is about 0.5 bar. If you take a parcel of the atmosphere at 1 bar, lets say in a balloon, and allow it to rise it will expand. As it expands it does work against the surroundings, and, from the conservation of energy, cools. So the atmosphere cools as you rise higher, because the pressure drops. The local temperature of the atmosphere does not depend on how close we are to the sun, but is a consequence of the greenhouse effect. Energy from the sun is absorbed by the Earth’s surface, and re-radiated at longer wavelengths. Some of this re-radiated energy is absorbed by atmospheric gases, leading to a warming of the lower parts of the atmosphere.