Questions about Climate Science  

I am interested to talk to someone who really knows the global warming science, preferrably someone working in the field. (Not some hippy who's read about it on the internet.) Can anyone condense the arguments down for me, or do I have to dig through the scientific literature myself? There seems to be growing suspicion of the anthropogenic argument, and I always am weary of scientists who are also activists---i.e. a large number of climate scientists seem to be making activist/alarmist claims. At the same time, certain parts of the polar regions are changing significantly, and it seems that there ARE documentable changes occuring.

Main questions: How do climate scientists estimate the effects of carbon and other greenhouse gases in the atmosphere? It's fairly trivial to show that carbon dioxide causes a greenhouse effect in a plexiglass box with a good thermometer, but how does this translate into a large scale system like the atmosphere?

How do climate models work, given that the climate is a nonlinear system? That is, very small changes in initial conditions lead to drastically different final states. This tells me that the computer simultations people do are highly dubious because they are either a) based on linear dynamics, and so have nothing to do with the climate, or b) non-linear and highly dependant on initial assumptions, and therefore not very predictive. Perhaps the difference is between predicting weather and predicting climate?

What evidence is there that the sun's power output has increased over the past century or so, resulting in the current epoch of warming? I heard some news clip on BBC about scientists disproving this, but have also seen evidence that the polar caps on Mars are also receding. Is there any validity to these claims?

This thread is likely to dissintegrate pretty rapidly, so we should have the intelligent conversation quickly before we are overrun I just want to discuss the science of this, not the politics. If you want to discuss the politics, go to the appropriate forum, please.