I think thats actually a worthy goal, presume the worst, hope for the best. But still, its safe to presume that we have a better than 80% odd of having an advanced civilization still in 100-500 years, when newer, more advanced technology may be able to mitigate to stabilize the problem better. If not, those warning signs for cave men saying "keep away" will probably be helpful. Either way, the costs of continuing to burn fossil fuels is very high - I can't decide if its too high or not - thats for people smarter than I to ponder upon.