I think that Gaianne isn't concerned about the effects of SO2 coming out (which it would do on a steady basis, regardless), but instead about the negative effects of losing its cooling effects all at once, causing abrupt warming that might well be more ecologically damaging than slow warming.

There is a valid concern here, though I think that Gaianne gives it too much weight for several reasons:

• First, treating the collapse of civilisation as certain claims more knowledge of the future than I think anyone can have at this point.

• Second, the scenario requires that a collapse be both world-wide and remarkably thorough, because putting SO2 in the stratosphere isn't very difficult. Since a generous estimate of the cost is 1/5000 of GWP, an economic collapse could be 99% complete, yet the cost would be no more than 2% of the remaining GWP. (And the job could be done with technology at the WWII level or less.)

• Third, I don't see any snap-back effects that are likely to be worse than the cumulative effect of decades of warm conditions, for example, polar melting.

(BTW, I usually avoid claiming that I know any particular person's unspoken thoughts and motives, or predicting that they will never reconsider an opinion. I'm much more comfortable making predictions that substantial groups will react in a particular way -- for example, I think that your prediction regarding Gaianne will surely prove true of many people.)

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