Temporal change of well-mixed greenhouse gases (CO2, CH4, N2O and CFCs) concentration is specified for the 20th-century climate simulation (20C3M). The total mixing ratio of CFCs are converted to equivalent CO2 and added to the CO2 concentration. The radiative forcing by the total halocarbons is evaluated as 0.3 W/m2 and equivalent to the 21 ppmv of CO2 at the level in 1990. The historical data used for the experiment are based on Hansen et al. (1998), which are available from http://www.giss.nasa.gov/data/simodel/ghgases/. The tabulated data are here.