Not exact matches
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).
(CO2 band is near the peak wavelength,
water vapor bands significant in stratosphere for wavelengths longer than ~ 25 microns and
between ~ 5.5 and 7 microns, and ozone
between ~ 9.5 and 10 microns, and CH4 and N2O
between ~ 7.5 and 8 microns — Hartmann p. 44 and 48, rough est. from graphs; signficant
stratospheric transparency remains in several of those bands except near the peak of the CO2 band, but especially
water vapor from 25 to 50 microns.)
«
stratospheric water vapor probably increased
between 1980 and 2000, which would have enhanced the decadal rate of surface warming during the 1990s by about 30 % as compared to estimates neglecting this change.
They argue that this «very likely made substantial contributions to the flattening of the global warming trend since about 2000» and that temperatures
between 2000 - 2009 would have warmed about 25 percent had
stratospheric water vapor remained constant.