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Asked by data499crow to Pete Webb, Martin M, Lauren G, Daniel E, Andrew L on 11 Jul 2024.
Question: why is it so cold at the top of a mountain when its closer to the sun???
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Pete Webb answered on 11 Jul 2024:
The top of a mountain is closer to the sun by only a tiny amount, so you don’t feel warmer climbing a mountain like you do sitting close to a fire! You actually feel colder because the air is thinner and doesn’t retain the heat reflected back from the Earth. The temerature of the vacuum of space is only 2 deg C above absolute zero.
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Martin McCoustra answered on 12 Jul 2024:
Basically, as you climb a mountain, the pressure drops as there is basically less atmosphere pressing down on you at greater altitude. We can see this pressure effect when we try to make a cup of tea… at sea level, water boils at 100 degC but at the top of Mt. Everest it will boil at only 68 degC. That isn’t hot enough to make a decent cup of tea!
Because in a gas like the atmosphere, pressure and temperature are linked by direct proportion, a drop in pressure means a drop in temperature. This means that the atmosphere cools as we climb up through it (mostly… as in some parts of the atmosphere like the stratosphere and thermosphere chemical processes warm the atmosphere because of the heat released by the chemistry). You can see the full temperature profile of the atmosphere here – https://en.wikipedia.org/wiki/Atmosphere_of_Earth. This is a result of what is called adiabatic expansion. The cooling rate is known as the adiabatic lapse rate and is around 7 degC/km in the lower atmosphere.
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