Deforestation increases atmospheric $\mathrm{CO}_2$ content by releasing carbon stored in organic matter and reduced primary productivity. So deforestation is one of the main factors contributing to global
warming other than green house gases. The various green house gases are $\mathrm{CO}_2(60 \%$ warming effect), $\mathrm{CH}_4$ (20\% warming effect) CFC ( $14 \%$ warming effect) and nitrogen oxide $\left(\mathrm{N}_2 \mathrm{O}, 6 \%\right.$ warming effect). Due to increase of $\mathrm{CO}_2$ concentration, the absorption of heat radiation also increase thus increasing the temperature. This increase in temperature may causes melting of glacier and polar ice caps, which is called global warming. This melting of glaciers and polar ice results in raising the sea level. Actually these green house gases absorbs infra red radiations (heat) of the sun like glass and thus traps the heat and does not allow it to radiate back to the space. They instead radiate the heat back to earth, thus causing increase in temperature.