This notion seems to incorrectly represent what climate science models are and how they are developed. If there were some way to "validate" them that everyone could generally agree upon, it would be possible to move this work to the domain of engineering. But each climate model varies quite a lot in its structure, dynamical equations, what simplifications it makes for numerical tractability, use of datasets and how to map them to model parameters. The role of climate scientists is to hash out which models are more sensible than others and to push the boundaries of accuracy and certainty with new methodologies.

This is why the best we can do from a policy perspective at the moment is model aggregation: that is taking tens of models computed by various research teams and combining them into policy recommendations along with uncertainty brackets. Distilling the state of current research into a policy digest is the role of the International Panel on Climate Change, which is currently in their sixth iteration of this process. You can keep up to date and read previous reports here. https://www.ipcc.ch/