In Kiehl and Trenberth 1997, they find a 155 W / m2 total greenhouse effect for approximately present -
day Earth conditions (among the approximations: surface is a perfect (isothermal **) blackbody, and the use a representative 1 - dimensional atmospheric column (instead
of seperate calculations for each location
over the globe at each time
over the
course of a
period of time sufficient to describe a climatic state — but note righthand side
of p. 200, just past halfway down the column)... a
few other things).