[kelnos]

Not the person you're replying to, but I think these two things are very different. I expect that the results of injecting substances into our upper atmosphere in large quantities are essentially impossible to model with high degrees of accuracy, and the consequences if things go wrong could be catastrophic. This freezing CO2 in Antarctica thing presumably does have some failure modes, but I imagine none of them are as comprehensibly terrible as if we were to screw up the atmosphere.