Ramaswamy, V., and M. M. Bowen, 1994: Effect of changes in radiatively
active species upon the lower stratospheric temperatures. Journal
of Geophysical Research, 99(D9), 18,909-18,921.
Abstract: A one-dimensional radiative-convective model is employed
to investigate the thermal effects in the lower stratosphere due to changes
in the concentrations of radiatively active species. In particular, we
consider the comparative influences due to species that exert surface-troposphere
radiative forcings of opposite signs. Two examples of such competing surface-troposphere
forcings are (1) increases in the well-mixed greenhouse gases versus increases
in tropospheric aerosols and (2) stratospheric ozone loss versus increase
in tropospheric ozone. The radiative equilibrium of the lower stratosphere
is perturbed both by the local changes in the concentrations of radiatively
active species and by the changes in species' concentrations occurring
in the troposphere and the middle/upper stratosphere. Perturbations in
the concentrations of each of the species, as considered above, leads to
a temperature decrease in the lower stratosphere. Relative to the well-mixed
greenhouse gases only case, simultaneous increases in these gases and tropospheric
aerosols cause a reduction of the net surface-troposphere radiative forcing,
thereby diminishing the surface warming. However, since tropospheric aerosols
contribute to a cooling of the lower stratosphere, the temperature decrease
there is enhanced above that due to trace gases alone, with the aerosol-induced
effects scaling approximately linearly with their optical depth. A complete
offset of the greenhouse gas surface-troposphere forcing by tropospheric
aerosols, while resulting in a null change in the surface temperature,
would double the cooling of the lower stratosphere. Increases in tropospheric
ozone would enhance the lower stratospheric cooling over and above that
caused by the stratospheric ozone depletion. This is in contrast to the
cooling and warming effects exerted upon the surface-troposphere system
by the stratospheric and the tropospheric ozone changes, respectively.
Tropospheric ozone increases of 20% or more can yield a lower stratospheric
cooling that is a significant fraction of the effects due to the observed
stratospheric ozone loss. Both the surface effects and the enhancement
of the lower stratospheric cooling scale approximately linearly with tropospheric
ozone increases.