Greenhouse gases refer to the sum of seven gases that have direct effects on climate change carbon dioxide (CO 2), methane (CH 4), nitrous oxide (N 2 O), chlorofluorocarbons (CFCs), hydrofluorocarbons (HFCs), perfluorocarbons (PFCs), sulphur hexafluoride (SF6) and nitrogen trifluoride (NF3) The data are expressed in CO 2 equivalents and refer to gross direct emissions