I think the bottom line about global warming is that we are deathly afraid of dynamics we don't understand. Our civilization is predicated on a very narrow set of conditions and we don't have the resources to handle major perturbations of those conditions.
It's not a question of how well our civilization can withstand significant changes just what level of disruption we are willing to withstand without doing something.
Taken to the extream to make a point, a 100 foot increase in sea level over 20 years would distroy an a silly amount of weath. However, a single 1 inch increase in sea level over 20 years would be hard to notice. It's not a question of 1 inch as ~0.1% of that increase = 0.1% of the dammage, rather it's a question of how much it costs to deal with the problem vs. starting over in a new area.
PS: Most of the time an inch is meaningless, but a dam that can take 10 feel might not take 10.08 feet. So, it's better to think of it as an increase in the number of local problems vs. a meaningless threat or some large scale doom. Granted, as you scale the increase more areas have larger problems.
