Terry Harper wrote:

However, I had heard about the reflection effects of H2O, of which there
is quite a lot in aircraft exhaust emissions. The URL Angus supplied
confirms that H2O in the stratosphere is thought to be a problem due to
the amount of back radiation it reflects being slightly higher than the
amount of incoming radiation it reflects - although scientists are far
from certain on this.

Because the atmosphere contains a lot more H2O than it does CO2, the effect
of water vapour is considerably more than that of CO2, but the processes of
condensation and re-evaporation tend to balance it out. CO2 absorption
depends more on photosynthesis than anything else, although some will
dissolve in water droplets.

Scientists know exactly what happens. Pseudo-scientists don't.

Scientists do not yet have all the information they need to fully
understand the effects of H2O in the stratosphere (nearly all of which
is in the form of tiny ice crystals in suspension).