CBSE Class 8 Answered

Undue increase in temperature of earth's atmosphere due to excessive greenhouse effect is called global warming. The green house gases such as CO₂, water vapours, methane etc. form a thick layer around the earth. When the heat rays coming from the sun fall on earth's surface, some of these rays are absorbed by earth and some are reflected back. Thus, cover of greenhouse gases does not allow these heat rays to leave earth's atmosphere completely. This effect keeps the earth's atmosphere warm. Rising amount of CO₂ causes more and more heat rays to be trapped in the earth's atmosphere. This results in excessive heating of earth's atmosphere, and therefore, temperature of earth's atmosphere rises. This results in global warming.