"...but the last 100 years is anamolous -- showing a 100 percent increase in CO2 over the peaks in the previous half-million year's ...." How do you get 100 percent increase ?
Using your own data in post 21 gives a 36 percent increase [ 380/280 = 36 % increase].
Using the peak of 300 ppmv in 323 Kyr BP gives 27 percent increase [380/300 = 27 % increase.]
ranges from 36 percent to 100 percent, as CO2 fluctuated between 180 to 280 for the last half million years. went outside the range 180-280 only in the last 100 years.