1.) Believe a solution still exists
2.) Believe that Australia of all the small populations on Earth would somehow matter if such a solution existed (no offense Australia, you matter in general)
3.) Believe that "thought" matters at this point. You might as well be telling people marching to the gallows to cheer up, nothing good can come of being all depressed. You might be right, but at least stop pretending that it's going to change the actual outcome.
2) My comments about Australia addressed the generally fuzzy thinking on this topic.
3) Again, there is no reason to think that the outcome is definite at this point. Clearly, in the worst case, technology should provide a solution. If the gloomiest projections turn out to be incorrect, for which there is mounting evidence, no mitigation may be needed at all.
I gave the concrete example of orbital sunshades, which are absolutely feasible given current engineering techniques. Another possible CO2 mitigation are iron-induced ocean algae blooms. Many other approaches have been suggested including nuclear powered CO2 sequestration in the Antarctic. I'm sure that many other innovative, technology based mitigations will be proposed over time.
I hope that clears things up for you.