The earth surface absorbs energy from the sun and radiates it back into the atmosphere. Socalled greenhouse gases are gases that, when present in the atmosphere, form a layer of insulation that traps the earth's outgoing heat. This causes the earth's overall temperature to become warm, a phenomenon originally known as the greenhouse effect, now more frequently called global warming or global climate change. The latter is a broader term that includes other atmospheric changes besides the greenhouse effect. Principal greenhouse gases include carbon dioxide (CO2), methane (CH4), ozone (O3), chlorofluorocarbons (CFCs), Nitrous oxides (N2O) and sulfur hexaflouride (SF6). While greenhouse gases are entering the atmosphere from both natural and human origins (the latter known as anthropogenic), the increase in human origins of such gases ...