Here's a really simplified bit on climate modeling that I put together a few years ago. I'm not sure if/where it might find a home on SKS.

(I really hate to use a car here, but most people are have direct experience with this.)

http://www.skepticalscience.com/climate_modeling_analogy.html

"(iii) how humans will respond to the threat of climate change; will will reduce our carbon emissions?"

This is not a part of the model, it is part of a scenario that is input to the model.