- Greenhouse gases are atmospheric gases that absorb and re-emit infrared radiation, trapping heat in the atmosphere and contributing to the greenhouse effect. - Major greenhouse gases include Carbon Dioxide (CO2), Methane (CH4), Nitrous Oxide (N2O), Water Vapor (H2O), and certain fluorinated gases. - Calcium Carbonate (CaCO3) is a solid chemical compound, the main component of materials like limestone and marble. It is not a gas and therefore not a greenhouse gas.