Greenhouse effect-What is green house effect

Green house effect definition,green house effect mechanism,it's causes and effects.
Today's crunch issue:
Greenhouse effect and it's causes and effects:
                                                                             The greenhouse effect is a process by which thermal radiation from a planetary surface is absorbed by atmospheric greenhouse gases, and is re-radiated in all directions. Since part of this re-radiation is back towards the surface, energy is transferred to the surface and the lower atmosphere. As a result, the temperature there is higher than it would be if direct heating by solar radiation were the only warming mechanism.
Greenhouse effect  is a process in which the energy coming from the sun heats the earth surface and and that energy is re-radiated by the earth surface in all directions.But the re-radiated energy does not go back because of the green house gases.The green house gases absorb that radiated energy from the earth surface and a part of this re-radiated energy again hits the earth surface and that energy is transferred to the lower atmosphere and as a result the temperature of the earth is more than it should be at normal circumstances.The rising of the temperature of the earth and it's surrounding due to green house gases is called the green house effect.
The greenhouse effect was discovered by French mathematician Joseph Fourier in 1824, first reliably experimented on by British physicist John Tyndall in 1858, and first reported quantitatively by Swedish scientist Svante Arrhenius in 1896.
Green house effect is caused by green house gases due to human activities.Earth’s natural greenhouse effect makes life as we know it possible. However, human activities, primarily the burning of fossil fuels and clearing of forests, have greatly intensified the natural greenhouse effect.

The main green house gases are:

• water vapor, 36–70%
• carbon dioxide, 9–26%
• methane, 4–9%
• ozone, 3–7%

Strengthening of the greenhouse effect through human activities is known as the enhanced (or anthropogenic) greenhouse effect.This increase in radiative forcing from human activity is attributable mainly to increased atmospheric carbon dioxide levels.
According to the latest Assessment Report from the Intergovernmental Panel on Climate Change, "most of the observed increase in globally averaged temperatures since the mid-20th century is very likely due to the observed increase in anthropogenic greenhouse gas concentrations.
Over the past 800,000 years,ice core data shows unambiguously that carbon dioxide has varied from values as low as 180 parts per million (ppm) to the pre-industrial level of 270ppm.
Greenhouse effect has also many bad effects on the whole world:

• Greenhouse effect is the main cause of global warming.
• Greenhouse effect raise the earth temperature causes glaciers and ice caps melting and rising of the sea levels.
• Rising of the sea level causes increase in natural disasters such as tsunami e.t.c.
• Rising sea levels could destroy many island.
• Melting of glaciers and ice caps would extinct many animal species living in that regions.

These are very few disadvantages of global greenhouse effect.And many of them are happening today.It could be much more if necessary steps are not taken.