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One possible answer is to look at how the then-state-of-the-art models in (say) 1990, 1995, 2000, etc, predicted temperature changes going forwards.
The answer, in point-of-fact, is that they consistently predicted a considerably greater temperature rise than actually took place, although the actual temperature rise is just about within the error bars of most models.
Now, there are two plausible conclusions to this:
It's not as simple as that. Most models give predictions that are conditional on input data to the models (real rate of CO2 production, etc.). To analyze the predictions from, say, a model developed in 1990, you need to feed the model input data from after 1990. Otherwise you get too wide an error margin in your prediction.
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