But since you brought up the Vostok ice core, I just have to show some interesting data plots from it:
Comment: the ice core shows that over the past 400,000 years, atmospheric CO2 concentrations varied between an upper bound of ~290 ppm and a lower bound of ~190 ppm. Climate scientists are real interested in determining what determined those bounds. Atmospheric CO2 concentration is currently at ~370 ppm -- 80 ppm higher than that upper bound! But there is a lag time in the climate system. So the problem facing the climate science community is; what is the rapid increase in atmospheric CO2 concentration, out of the 400,000 year bounds, going to cause?
Here's the other plot (at the far right edge you can see how high current atmospheric CO2 concentrations are):
Comment: this shows that CO2 and temperature have been linked over the past 400,000 years. Most studies show that the warming was driven by other factors and that CO2 concentration responded to warming or cooling. The problem facing climate scientists now is that the CO2 rise is occurring in a nominally "stable" temperature regime, so it will be a forcing factor for climate change. How much the change will be, and how fast, is very uncertain.
This is the type of data I'd like to discuss with ancient_geezer. I just need some time to prepare a full treatment.