What is the greenhouse effect?

In a greenhouse, the air gets heated up because the warm rays of the sun get trapped by the roof and the walls and are not reflected outwards completely. This situation is comparable to the conditions currently prevailing on the Earth. The layer of the atmosphere, which acts like the glass roof, contains greenhouse gases, such as water vapour, carbon dioxide, methane, nitrous oxide, and ozone, in appropriate amounts to keep the Earth comfortably warm. Due to irresponsible human activities, the carbon dioxide content has increased by 20% and methane content by 90%. As a result more heat is getting trapped and making the Earth warmer than usual. The increased temperature is causing the ice of the polar caps and glaciers to melt; this has led to a rise in sea levels and drastic climate changes all over the world.