Definition of Global Warming

It is important to understand and discuss the significance of global warming. Global warming is also known as the "Greenhouse effect". The "Greenhouse Earth" is surrounded by a shield of atmospheric gases, rather than a glass or a plastic cover. The air that makes up our atmosphere consists primarily of nitrogen and oxygen molecules (N2 at 78% and O2 at 21%). A large number of "trace gases" make up the remainder of air's composition. Many of these, including carbon dioxide (CO2) and methane (CH4) are the so called "greenhouse" gases.

If you have ever felt the piercing cold of the clear winter night sky and wondered why you feel warmer on a cloudy winter night, you have experienced the atmospheric greenhouse effect firsthand. Physics tell us that any object warmer than absolute zero will radiate energy. Cooler objects emit longer waves (in the infrared region) while hotter ones radiate shorter wavelengths. Our sun, powered by its hot, nuclear fusion reaction, produces radiant energy in the visible and ultraviolet regions with relatively short wavelengths. Of the sunlight that strikes the earth, about 70% is absorbed by the planet and its atmosphere, while the other 30% is immediately reflected. If the earth did not re-radiate most of this newly absorbed energy back into space the world would continue to get warmer. Instead, an energy balance is maintained.

The earth is about 60 degrees Fahrenheit (33 degrees Celsius) warmer than it would be if it did not have the atmospheric blanket of greenhouse gases and clouds around it. Clouds and greenhouse gases keep the earth warm. Once warmed, their molecules then radiate a portion of this heat energy back to earth, creating more warming on the surface of our planet. It is this radiation which causes atmospheric gases to move back to earth that scientists call the "greenhouse effect".