We can make good estimates of global temperature so can estimate planck radiation (on global level), good estimates of albedo from ice extent, reasonable estimates of evaporation and convection from temperature contraints, now try closing that surface budget with GHG. (theinconvenientskeptic.com)
And BTW, the true planck weighted tau was first defined and introduced in the Appendix of my 2007 paper, and so far it is not computed by any other LBL code but HARTCODE. (scienceofdoom.com)
function ri = planckm (w, t) % planck function for matrix of wavelength, w and temp, t % result in spectral intensity [ww tt] = meshgrid (w, t); ri = 3.742 E8. (scienceofdoom.com)