WHT, I am not sure what you are arguing:
Do you agree that your charts of the Greenland ice cores show much faster rates of warming in the past 8,000 years and even faster in the past 20,000 years than anything we have encountered in the past 200 years? (previously you acknowledged this is what they show).
So what that we are at 400 ppm? That is a very low CO2 concentration in Earth history, and the Earth is at a temperature well below its “normal operating temperature”. So I don’t see why that is scary. In fact, it may be good to be rising above the level at which life would be virtually wiped out (i.e. about 170 ppm).
The James Hansen Figure 1 here http://www.columbia.edu/~jeh1/mailings/2011/20110118_MilankovicPaper.pdf shows the planet is in a dangerous long term trend. It is getting colder and CO2 concentrations are reducing. That suggests catastrophe if that continues. Playing devils advocate, we could argue that raising CO2 levels is a precautionary step (good risk management) rather than an irresponsible and dangerous act.
If not for man’s CO2 contribution, how much colder would you predict the Earth would be in 200 years from now?