A gradual increase in the overall temperature of the earth's atmosphere generally attributed to the greenhouse effect caused by increased levels of carbon dioxide, chlorofluorocarbons, and other pollutants. Global warming, also referred to as climate change, is the observed century-scale rise in the average temperature of the Earth's climate system and its related effects. Multiple lines of scientific evidence show that the climate system is warming.
Global warming happen because release of harmful greenhouse gases into the atmosphere, some gasses can't past the atmosphere that make the gasses trapped. There are several caused of global warming:
Deforestation
Trees and plants store carbon, they also produce oxygen and are natural prevents against global warming. When forest are cleared carbon dioxide release back to the atmosphere. The more forest are cut, the more carbon dioxide are back to atmosphere, and it is effect to earth's atmosphere.
Methane release
Methane is a greenhouse gas that occurs naturally when organic matter is broken down by bacteria when very little oxygen is present. Methane is emitted during the production and transport of coal, natural gas, and oil. Methane emissions also result from livestock and other agricultural practices and by the decay of organic waste in municipal solid waste landfills.
CFC's
Chlorofluorocarbons (CFC's) are a group of compounds which contain the elements chlorine, fluorine and carbon. CFC's are unlikely to have any direct impact on the environment in the immediate vicinity of their release.
As VOCs, they may be slightly involved in reactions to produce ground level ozone, which can cause damage to plants and materials on a local scale. At a global level however, releases of CFC's have serious environmental consequences. Their long lifetimes in the atmosphere mean that some end up in the higher atmosphere (stratosphere) where they can destroy the ozone layer, thus reducing the protection it offers the earth from the sun's harmful UV rays.
Nitrous Oxide
Nitrous oxide, commonly known as laughing gas or nitrous, is a chemical compound , an oxide of nitrogen with the formula N2O. Nitrogen oxide occurs naturally and also as a result of man's activities. In environmental conditions it is a colorless, sweet smelling gas. Nitrous oxide also damages the ozone layer, thus reducing the protection offered from harmful UV sun rays.