Sorry, I responded to someone else making a similar point. In this case, the author adopts a bad-case perspective. He isn't necessarily right. Number one, presuming this is Centigrade, the majority of the models converge around 2-3 C for warming by 2100. (I actually happen to think that the quote is for Fahrenheit degrees, because the maximum - highly unlikely - predictions are 6 C or 10 F.
Review this long thread, and look for responses regarding James Hansen's alternative scenario.
Furthermore, there have been discussions of carbon sequestration, which could help. But the main determinant is economic trajectories and energy use.
Yes, change is coming. Action now and soon might be able to prevent the more serious detrimental changes. However, if plans aren't made now to enable actions in a few years (like increased use of biofuels), then the window for effective action will get smaller and smaller.
The market is driving some of these changes. That's a start.
Okay, so we can run around doing drastic things now that MIGHT prevent SOME things... or we can be a little more sanguine and realize that:
1) Scientific models are famous for being inaccurate and
2) Climate change happens so slowly, humanity will probably adapt to it just fine.
Sorry, I'm still going with my scenario: it is more reasonable to adapt than to flail about struggling to prevent. Especially if our attempts at preventing the inevitable will create all sorts of unintended crises that will then have to be dealt with. Now, if we want to develop alternative methods of fuel etc to free us from the Middle East, I'm all for it. But that's not one of those "narrow window, hurry hurry" things.