This tends to speak well to your posed question "what happens if global warming is wrong?" The title of the video is so hyperbolic it isn't even worth arguing about. http://www.youtube.com/watch?v=zORv8wwiadQ
The arguments are sound and logical though.
Very week argument really.
For starters, column A should both have economic depression (since the cost is there no matter what). The difference being that row 2, column A would avert enviromental catastrophe.
False: Climate Change isn't man made nor is any significant issue occurring.
True/Doom: Climate change is occurring but it's NOT caused by man.
So you thus add an even worse scenario: We spend the money, cause a global depression and STILL get an environmental catastrophe.
And THAT is the issue that skeptics worry about that the strawman video ignores.