The models do nt attempt to predict weather, are poor at regional prediction and have no skill at even decadal level prediction. (skepticalscience.com)
I understand that the models seemed to have some problems at the decadal level with the early 40's spike (explained by el Nino anomalies?) (realclimate.org)
[71][72] Because of the way air is trapped in ice (pores in the ice close off slowly to form bubbles deep within the firn) and the time period represented in each ice sample analyzed, these figures represent averages of atmospheric concentrations of up to a few centuries rather than annual or decadal levels. (en.wikipedia.org)