This integral can be done at the OD = 1 point, because that is
the photosphere radius for the IR, and for the non-GHG frequencies it doesn't matter where you do the integral.
Not exact matches
The Sun's
radius is measured from its center to the edge of the
photosphere.
You say that where the OD = 1 point, which represents the
radius of the
photosphere for IR, and as the concentration of CO2 increases, this
radius shifts upwards.
But the downward radiation, which is sourced by the upper atmosphere, does not: At the
radius of the old
photosphere, before the addition of the GHG, the downward radiation was rather small, because there wasn't much of the sourcing GHG above it.