If then how do we know the issue is related to his climate change opinion? Could just as easily have been a budget issue.

His web page at Oregon State suggest he was simply an Instructor. No indication that he was in line for professor status. Likely just a non tenure track instructor hired to fill a vacant slot about the time that budgets began hitting the fan. They can be let go at will.

Also, woefully weak on publications (like 1, and he was 3rd author there). No mention of texts either, and books would be listed in ones bio. Not a mover and shaker in the science world at all.

If he has/had tenure, the firing should have involved a bit more procedure.