Many publications and posts on blogs still refer to the so-called radiation window in a global energy balance as 40 W/m2. The correct figure is 66 W/m2 see the extract below from a presentation by Dr Noor van Andel to KNMI in Sept 2010

**Click on image to enlarge**

By using the value of 66 W/m2 there no need to have a figure for backradiation at the Earth surface as incorrectly put into the cartoon of GLobal Engery balance made up by Trenberth et al

Energy into surface

168 W/m2

Energy away from surface

Convection and conduction 24 W/m2

Evaporation 78 W/m2

Radiation window 66 w/m2

Total away 168 W/m2