The Greenhouse effect
Greenhouse gases in the Earths atmosphere absorb infrared radiation sent out from the Earths surface. The main ones are water vapor, carbon dioxide, methane, nitrous oxide and engineered chemicals including chlorfluorocarbons.
By absorbing this radiation emanating from the surface, the gases trap heat in the lower atmosphere. Without the natural greenhouse effect, the earths surface temperature would be around minus 19 degrees Celsius, rather than the global average 15 degrees Celsius.
Most greenhouse gases are natural and provide an atmospheric balance that keeps the Earth at its current temperature. But in the early 1960s, scientists noticed that carbon dioxide concentrations, in particular, were increasing. Scientists began to fear that if the concentrations of human-made greenhouse gases continued to increase, the average temperature of the Earth would get warmer. This could cause changes in the weather and a rise in sea level that would erode beach regions worldwide. This phenomena is called The Greenhouse effect or Global Warming.
Carbon dioxide, the second most important greenhouse gas, is added to the atmosphere, both naturally and unnaturally. It has been added naturally by volcanoes throughout the Earths history, and cycled through the many natural pathways carbon follows in nature. But CO2 is also added unnaturally as a result of current human activity. The increase of carbon dioxide in the atmosphere is caused mostly by the inefficient and increased burning of coal, oil and natural gas as well as the destruction of the rain forests.