Greenhouse gas

From Envirowiki

A Greenhouse gas is a gas that contributes to the greenhouse effect.

Basically, most gasses with molecules of three or more atoms are greenhouse gasses, of varying intensity. Basically, greenhouse gasses are transparent to high-frequency electromagnetic radiation (such as anything with a higher frequency than visible light), which enters the earth's atmosphere. This radiation then hits objects which are opaque to it, such as most solids, and is reflected, or absorbed. Some of the the energy that is absorbed, is re-radiated as lower-frequency electro magnetic radiation, which has more thermal energy, such as infra-red. Greenhouse gasses are opaque to these lower frequency radiations, which means that they are absorbed, and stay in the atmosphere, or reflected, and re-enter solids, or liquids (i.e. Land or Sea). The resultant effect is an over all warming of the globe.

Glass acts in a similar way, though it's a solid, not a gas. Hence the name.