I very much agree with your skepticism when it comes to believing the results of large scale simulations of complex systems. I personally think many people incorrectly transfer the certainty that we have of the underlying phenomena to the results of these complex simulations. No rational person disputes the direct effects that CO2 has on the absorption and re-emission of IR but once this is included into hugely complex simulations, I believe a very large degree of skepticism is warranted.
However for almost exactly the same reasons I maintain some skepticism over the simulation results, I am personally very strongly in favor of minimizing man's impact on the environment. Precisely because it is a hugely complex system and I don't believe we can predict the effects of any changes we make to the environment.
Depressingly, it seems that the chances of persuading America to really embrace a serious reduction in its CO2 emissions (especially if the Republicans get any more power) is extremely small. And even if America were on-board getting world-wide consensus would still be difficult in the extreme.
It may very well be that the only option we have is deal with consequences of climate change as they arise. This will likely be more expensive than if we were investing in reducing our impact now but the way politics works the world over means that people are very reluctant to take short-term pain for long-term gain. And it should be remembered that even if the climate changes even faster than has been predicted, it will still be a gradual process, and countries will adapt to it the best way they can as and when it is required. By this I merely mean to dispel the idea that some people seem to have of utter catastrophe if action is not taken.