Greenhouse gases are atmospheric gases that absorb and re-emit infrared radiation, trapping heat in the atmosphere and contributing to the greenhouse effect. Common greenhouse gases include Carbon dioxide (CO2), Methane (CH4), Nitrous Oxide (N2O), Chlorofluorocarbons (CFCs), and water vapor (H2O). Argon (Ar) is a noble gas that is chemically inert and does not absorb infrared radiation in the same way as greenhouse gases, therefore it does not contribute to the greenhouse effect.