That is a good question, and the answer is not simple. A necessary conditions for water vapour in a given air-parcel to condense out is that relative humidity should be 100%, or the less known concept of a dew-point temperature is the same as ambient stratospheric temperature.
In other words, it is possible that H2O vapour concentration did not reach saturation levels at the given air temperatures (stratosphere). However, due to passage of waves through that region it could, locally, trigger condensation. However, the actual micro-physics of having enough condensation nuclei, the physics of growth and falling of micro-dropplets, and large scale circulation and winds complicates to estimate the actual time scale of residence against condensation.
Even the original article does not try to touch any of these aspects, rather create a 'narrative' without any quantitative (even back of envelope) estimates. But one has to appreciate that 145 Tg of water injected into the stratosphere in a single episodic release is mind-blowing number.
There is apparently a kind of bacteria that can cloud seed. I don't recall how it gets up into the air, but it has some biochemistry that increases the dew point by a few degrees celcius, and then rides the rain back to the ground.
We may find that seeding the stratosphere with one of these bacteria, especially if this happens again when we are farther down the Climate Change rabbit hole, is more ecologically sound than stuffing aerosols up there.
Seems the likely result of this could be atmospheric systems getting a boost in energy & dynamics in ways that would lead to both more severe weather and increased precipitation in certain storms. It also might make some storms harder to predict.
This volcano can be responsible for "10% of the entire water content of the stratosphere",
and "The water will probably remain in the stratosphere for half a decade or more",
and this will "eat away at the ozone layer".
We've known that H2O is what most absorbs infrared in the atmosphere for 150 years; the thing is that how much H2O exists in the atmosphere is a function of temperature, and with the exception of an event like this volcanic eruption, only of temperature. So H2O can't be the ultimate cause of variation in temperature because it is the effect. It is the (small) increase in temperature from the increase in CO2 that makes it possible for the atmosphere to hold more H2O which in turn dramatically amplifies the the increase in temperature.
None of this is in doubt, none of this is new. The Swedish scientist Svante Arrhenius[0] modeled this feedback to a reasonable approximation in 1896.
As for the H2O from this eruption, it may seem like a lot of water, and relative to the normal amount in the stratosphere it is, but that's because of all the H2O in the atmosphere the stratosphere contains only the tiniest fraction (because it's cold up there). Most of the H2O is near the ground, and that's where most of the IR absorption happens. So this thing isn't going to have a big effect on the greenhouse effect, which is why they talk more about what it might do to the ozone layer.
And as for the paper you cited... looks like it was written by a bunch of old (retired) engineers who have absolutely no clue about actual atmospheric science.
My understanding of that paper is that it does not dispute the feedback effects, but rather seeks to quantify them, specifically the climate sensitivity for CO2, CH4 and N2O.
> And as for the paper you cited... looks like it was written by a bunch of old (retired) engineers who have absolutely no clue about actual atmospheric science.
Surely if their approach is valid, and the maths is correct, then who they are, their age, and their field of expertise is irrelevant?
Now admittedly I've only got part way through the paper, but I've yet to find an error in their maths.
I therefor assume that either you have found an error in their maths, or that you can state why their approach is invalid. I'd appreciate it if you could explicitly state those failings.
