Global Warming is the increase of Earth's average surface temperature due to effect of greenhouse gases, such as carbon dioxide emissions from burning fossil fuels or from deforestation, which trap heat that would otherwise escape from Earth.Global warming begins with the greenhouse effect, which is caused by the interaction between Earth's atmosphere and incoming radiation from the sun.Human-caused global warming occurs when human activity introduces too much of certain types of gas into the atmosphere. More of this gas equals more warming. The atmospheric gases primarily responsible for the greenhouse effect are known as "greenhouse gases" and include water vapor, carbon dioxide (CO2), methane (CH4) and nitrous oxide (N2O). The most prevalent greenhouse gas is CO2.CO2 makes its way into the atmosphere through a variety of routes. Burning fossil fuels, for example, releases CO2. Deforestation is also a large contributor to excessive CO2 in the atmosphere.It leads to melting of ice, rise in temperature of the atmosphere,depletion of ozone layer etc
1 5 1

                  Global warming is the increase in the average temperature of the earth's near-surface air and oceans since the mid 20th century. The generally accepted theory about global warming is that the release of greenhouse gases from the burning fossil fuel and from land-use is responsible for the recent temperature rise.

                  The increase of certain gases in the atmosphere trap energy which would otherwise escape into space. These gases called greenhouse gases include carbon dioxide, methane, nitrous oxide, chloroflourocarbons and ozone in the lower atmosphere. Many natural and man-made gases contribute to the greenhouse effect that warms the earth's surface. Of all those, the increasing concentration of atmospheric carbon dioxide is the most likely cause. When more heat is trapped in the atmosphere, this makes the earth hotter.

                   The Earth has an umbrella of gas to protect it from the dangerous ultraviolet radiation of the sun. This umbrella is known as the Ozone layer. Unfortunately the pollutants and chemicals can destroy the ozone upsetting the balance in the almosphere. When this happens the ozone layer is depleted and the amount of ultraviolet rays reaching the earth's surface increases. As  a result of human activities like smoke from factories and vehicles being emitted, the composition of the atmosphere has changed and ozone layer is now under threat. Recent satellite pictures have shown quite clearly that there is a hole appearing in the ozone layer over the Antarctic Pole. More UV rediation reaching the Earth can affect human health by causing diseases like cancer and various eye-disorders.

                        As we know that 'greenhouse effect' and 'ozone depletion' results in global warming we have to act promptly to check the causes leading to them. For this human activities like burning of fossil fuels have to be replaced by harmless methods. Planting plenty of trees can also help to a certain extent to reduce pollution and global warming.