Well, not my field, so I may be totally off base. But if someone simulated a car engine (for example), there is solid science that allows reasonable prediction. And you can run physical tests to confirm the results predicted by the model. I consider this legitimate science.
But Global Warming and Asteroid Strikes involves a lot of guesswork and cannot be verified by physical tests. I don’t see much value in such sims.
Seems to me the amount of unknown variations and just plain lack of complete knowledge of how our planets weather system works and our short term knowledge of the suns cycles and such would make any computer model useless.
For large scale, there are the prehistory impact events that present some evidence which can be processed. On a small scale, impact events created in a lab setting have established a separate body of information. The study of contact nuclear detonation blasts finds parallels with effects generated by collision / impact of meteorites. All of this contributes to a physics model adapted from the national lab’s prior nuclear weapons model.