As a scientist who has often used modeling in research, I concur that models have to be regarded with great suspicion -- unless there is LOTS of broad empirical data to back it up. It reminds me of the old saying about Magnetohydrodynamics calculations:
"It takes a genius to get computational results from these equations -- and a fool to believe them."
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And MHD of any earthborne system is child's play when compared with the vastly greater complexity of global climate/ weather. Even the Sun is more uniform and is probably more calculable than Earth, due to the Earth's continents and diverse terrain and diverse components.
By the way... is MHD of any use in describing auroras?
I don't know. I'm basically a solid-state physicist (mostly theoretical) and digital signal-processing guy.