Greenhouse Gas: GHGs cause climate change by trapping heat in the atmosphere, and their cumulative total make up a company’s carbon footprint. The main GHGs are water vapor (H2O), carbon dioxide (CO2), methane (CH4), nitrous oxide (N2O), hydrofluorocarbons (HFCs), perfluorocarbons (PFCs), and sulphur hexafluoride (SF6).