A parameterization scheme for carbon dioxide 15 μm band absorption and emission is developed based on the line-by-line transmittance data presented by Fels and Schwarzkopf (1981). We derive two polynomial equations to represent the broadband emissivity as functions of the temperature and pressure corrected path length. A detailed error analysis has been performed, and the root mean square errors are shown to be on the order of 5 and 7.5% for the lower and upper atmosphere cases, respectively. Cooling rates calculated from the emissivity parameterization approach show errors within about 5% when they are compared with those computed from exact line-by-line integrations.