Greenhouse gases are those gases which has the capacity to trap out going long wave terrestrial radiation in the lower atmosphere where they are largely concentrated. These gases are CO2, Methane, CO2 NO and water vapour. They by increasing the temperature of lower atmosphere, thereby increase the temperature of earth surface. It has led in increase in sea level across the world.

Floods, droughts, change in hydrological cycle, desertification are all the outcomes of greenhouse effect. It has to depletion in bio­diversity. We have, seen in the past few decades the CO2 level has increased manifold visa-vis its earlier level

Thus, observation say that average global temperature has raised by 0.6°C in last 130 years and Global sea level has increased by 10-15. cm over past 100 years.