I'm just going to come out and say this: as depressing as global warming is, I'm not that worried about it. Sure, corals are screwed, though some hardier species will probably survive and replace those we loose; significant, heavily populated portions of the world will probably be made unliveable through flooding or intensification of droughts, including low-lying areas of Bangladesh and other Southeast Asian countries through flooding and the Southwestern US through drought; and it's likely that some amount of upheaval will accompany the changes in climate that are coming. We're going to see a couple of degrees of warming even if we stop emitting CO2 right now--completely--which may be enough to trigger some of the smaller, less-severe problems global warming poses (particularly the spread of disease). If we choose to try and mitigate global warming by throwing tons of sulfur dioxide aerosols into the stratosphere (where acid rain fallout is less of a concern) we'll have to shoot the equivalent of hundreds of buses worth of sulfur dioxide at least 10 km into the atmosphere and all along the equator, or we'll risk all the warming we would have seen happening even faster than it's happening now. CO2 capture is thermodynamically possible, but will require huge amounts of energy to implement, decreasing the efficiency of all power plants that employ it.
And yet, I'm not worried. The cynical side of me says that's because if I really cared, it would be debilitating.
This article by Jared Diamond points out that the level of consumption of resources is a huge problem, and one that we could at least mitigate if we were to cooperate more effectively in using resources in a sustainable manner and in conservation efforts. This sort of thinking gives me hope that we can find solutions to looming environmental problems, if we can be reasonable and think critically and hard about what we really value as a society. I suspect the same thing is true when it comes go CO2 emissions and global warming. We really are at some point going to have to confront the environmental problems our American lifestyle generates; the question is whether we will do it willingly and clean up our act before we are forced to, or whether we will wait until we have no choice and suffer the hardships that will certainly result. I hope as a society we're smart enough to choose the former option rather than the latter.