What Is the Greenhouse Effect?

THE greenhouse effect describes atmospheric heating that many scientists fear is already affecting the entire planet. If you've ever parked your car in the hot summer sun with all the windows closed, you got a taste of the greenhouse effect. The windows of your car are transparent to the sun’s rays, which quickly warm the interior. But the hot air inside the car cannot escape, and neither can the heat itself. Why not? Because heat is given off in the form of infrared rays, which are invisible to the eye but can be felt on the skin, for example, when you stand near a fire. The same glass that lets visible light in prevents much of the invisible infrared radiation from getting back out. So the temperature inside your car goes up and up.
The earth’s atmosphere is similar to the glass in your car’s windows. It readily admits visible light but blocks a great deal of invisible radiation, including infrared and ultraviolet light, as well as X rays. In general, this blocking is a good thing. Ultraviolet light and X rays are quite dangerous and are believed to cause cancer. However, too much of a good thing, a runaway greenhouse effect could mean mass starvation as grain belts turn to dust bowls. It could also mean superkiller hurricanes powered by extra warm oceans, rising oceans flooding coastal areas, rampant skin cancer brought on by an eroding ozone layer, and untold human misery.