Warming must occur below the tropopause to increase the net LW flux out of the tropopause to balance the tropopause - level forcing; there is some feedback at that point as the stratosphere is «forced» by the fraction of that increase which it
absorbs, and a fraction of that is transfered back to the tropopause level — for an optically thick stratosphere that could be significant, but I think it may be minor for the Earth as it is (while CO2 optical thickness of the stratosphere alone is large near the center of the band, most of the
wavelengths in which the stratosphere is not transparent have a more moderate optical thickness on the order of 1 (mainly from stratospheric water vapor; stratospheric
ozone makes a contribution over a narrow
wavelength band, reaching somewhat larger optical thickness than stratospheric water vapor)(in the limit of an optically thin stratosphere at most
wavelengths where the stratosphere is not transparent, changes in the net flux out of the stratosphere caused by stratospheric warming or cooling will tend to be evenly split between upward at TOA and downward at the tropopause; with greater optically thickness over a larger fraction of optically - significant
wavelengths, the distribution of warming or cooling within the stratosphere will affect how such a change is distributed, and it would even be possible for stratospheric adjustment to have opposite effects on the downward flux at the tropopause and the upward flux at TOA).
What they found was a drop in Escaping Infra Red radiation at the PRECISE
wavelength bands that greenhouse gases such as CO2 with H2O, CFC's,
Ozone, Nitrous Oxides, & methane (CH4)
absorb energy.
The basic principle of the DIAL technique is to transmit two short laser pulses vertically into the atmosphere, one having a
wavelength in an absorption band of
ozone (typically 308 nm) and the other not
absorbed by
ozone — or not so strongly
absorbed (typically 355 nm).