Relative contribution of various greenhouse gases to total global warming is
$\bullet \; CO_2 = 60 \%$
$\bullet \; CH_4 = 20 \%$
$\bullet \; CFC= 14 \%$
$\bullet \; N_2O = 6 \%$
$\Rightarrow \; $ Therefore $CO_2$ and $CH_4$ are the major greenhouse gases