The gases in our atmosphere allow the sun’s energy (shortwave radiation) to pass through and heat the earth’s surface. The earth in turn radiates the energy back to the atmosphere in the form of long-wave infrared radiation. This process causes the net warming of the earth and atmosphere and is sometimes referred to as the natural greenhouse effect. The glass of a greenhouse works in a similar way, letting in short-wave radiation but preventing long-wave radiation from escaping and thus the air in the greenhouse is warmer that the air outside. The major greenhouse gases are Water Vapor (H2O), Carbon Dioxide (CO2), Methane (CH4), Ozone (O3) and Nitrous Oxide (N2O). This natural greenhouse effect enables the earth to maintain an average of 15 degrees Celsius; without this effect the surface temperature would drop drastically to -18 degrees Celsius and the earth would be unable to support life as we know it. Humans have however altered the chemical composition of the atmosphere by releasing large quantities of greenhouse gases - primarily carbon dioxide, methane, and nitrous oxide. These gases are trapping more energy and reflecting it back to earth. This is having an effect on global atmospheric temperatures. This is often referred to as the human-induced greenhouse effect.