If warm air rises why is it colder at 10000 feet than it is at sea level

Question

If warm air rises why is it colder at 10000 feet than it is at sea level

Answer 1

First answer was right on, but I would add that if you see pictures of old pilots, say WWII or earlier, they all are wearing fleece jackets, scarves, gloves and such.  Its cold up there and military planes of those years did not have cockpit heaters.

Answer 2

As you go up in altitude from the surface of the earth, the air cools at a

fixed rate. This is called the "lapse rate," and for unsaturated air, that

rate is about 5 deg. C. for each thousand feet of altitude. For saturated

air, the rate is about 3.5 deg.C. for each thousand feet of altitude.

Answer 3

Because as the warm air rises it's pressure decreases.  It is a physical effect that in general, as air pressure decreases, the temperature of that air will decrease.