the earth is surrounded by atmosphere, in the atmosphere on the stratosphere layer between 15 - 50 km is made of gases such as CFC, methane, carbon-di-oxide, etc. these gases are capable of observing the sun rays. The sun ray reaches the earth surface and is redirected as infra-red rays. The gases couldn't send the infra-red rays out. As a result, the heating property of infrared rays makes the earth warm. Due to increased emission of carbon-di-oxide these gases absorb sun rays and prevent the infra-red rays from moving beyond. This phenomena increases earth temperature and is called global warming.
The effect of this is
1.)POLAR ICE CAPS MELTING
2.)CHANGE IN RIVER PATTERN
3.)INCREASE IN COMMUNICABLE DISEASES
5.)SEA LEVEL RISES