what are the two most important greenhouse gasses?
['Water vapor (H. 2O)', 'Carbon dioxide (CO. ... ', 'Methane (CH. ... ', 'Nitrous oxide (N. 2O)', 'Ozone (O. ... ', 'Chlorofluorocarbons (CFCs)', 'Hydrofluorocarbons (includes HCFCs and HFCs)']