To illustrate the atmosphere, picture yourself on top of an ocean of water that is about four hundred miles deep. Assuming one could survive the depths of this ocean, you rapidly descend to the bottom in a submarine. On the bottom of the ocean you leave your sub to observe the changing ocean above, noticing that it is cooler down here than it was at the top. Imagine the ocean above as our atmosphere, and you are now on the bottom of the ocean of air. In general, the density and temperature of the air decrease with elevation.
Phenomena associated with the weather occur in the troposphere.
The gases in the air are part of natural earth cycles. Several factors affect the amount of radiation that is absorbed by the earth at different places. Because the earth is a sphere, the sun's rays strike different places at different angles. Near the equator the sun passes almost directly overhead. North and south of the equator, the surface of the sphere curves away from the sun.