Global warming prediction with modtran at 20 km
your image should have been seen here!
  • frame 1. An increase in CO2 from 0 ppm to 300 ppm reduces outward radiation, which by definition is a positive radiative forcing, with ΔF=28.32 W m-2.
  • frame 2. An increase in CO2 from 300 ppm to 600 ppm produces radiative forcing of ΔF=3.39 W m-2.
  • frame 3. A constant temperature increase ΔT=1.02 K in the troposphere (from 0 through 11 km) is able to restore the outward infrared irradiance F↑ at 20 km to its original value.
  • frame 4. If relative humidity remains constant (and thus specific humdity rises) as temperature increases, then ΔT=1.50 K.
See also the exercise for restoration of balance at 70 km. Note the CO2 band at 667 cm-1 is saturated at 300 ppm, except for the wings of the band. Hence the radiative forcing for changing from 0 ppm (gray) to 300 ppm would be ΔF=28.32 W m-2; changing radiative forcing from 300 ppm to 600 ppm is ΔF=3.39 W m-2.