2. If it were not for greenhouse gases trapping heat in the atmosphere, the Earth would be a very cold place. Greenhouse gases keep the Earth warm through a process called the greenhouse effect. 1.The Earth gets energy from the sun. 2.Earth absorbs some of this energy and heats up. 3.The Earth cools down by giving off infrared radiation. 4.Greenhouse gases absorb some of the radiation before it can escape and this warms up the atmosphere.

3. 1.Water Vapor (H2O) 2.Carbon Dioxide (CO2) 3.Methane (NH4) 4.Nitrous Oxide (N2O) 5.Ozone (O3) 6.Chloroflourocarbons (CFCs) Greenhouse gases absorb this energy, thereby allowing less heat to escape back to space, and 'trapping' it in the lower atmosphere. Some greenhouse gasses are natural, while others are man- made.

4. Water Vapor is the most abundant greenhouse gas in the atmosphere As the temperature of the atmosphere rises, more water is evaporated from Earth. The air is able to 'hold' more water when it's warmer, leading to more water vapor in the atmosphere.

5. Carbon Dioxide is produced naturally in the our atmosphere. However, humankind has altered the natural carbon cycle by burning coal, oil, natural gas and wood Carbon dioxide was the first greenhouse gas demonstrated to be increasing in atmospheric concentration

6. Methane (CH4) is an extremely effective absorber of radiation. Methane has both natural and human sources of production. produced by microbial processes in soil and water, including those reactions which occur in fertilizer containing nitrogen

7. Existing in a broad band, commonly called the 'ozone layer', a small fraction of this ozone naturally descends to the surface of the Earth. However, during the 20th century, this tropospheric ozone has been supplemented by ozone created by human processes.

8. Chlorofluorocarbons (CFCs) have no natural source, but were entirely synthesized for such diverse uses as refrigerants, aerosol propellants and cleaning solvents. They destroy good ozone in the stratosphere. Their long atmospheric lifetimes determine that some concentration of the CFCs will remain in the atmosphere for over 100 years.