The greenhouse gases in Earth’s atmosphere are: Water vapour (H2O), Carbon dioxide (CO2), Methane (CH4), Nitrous oxide (N2O), Ozone (O3) and Chlorofluorocarbons (CFCs). Methane is an important greenhouse gas with a global warming potential of 34 compared to CO2 over a 100- year period, and 72 over a 20- year period.