Major pop psychology generalisations incoming:
I think the OP has the psychological motivation of doomers wrong.
Doomers are just deniers that can no longer maintain the everything is fine reasoning.
The problem is, this does not actually change their position.
Which is "I do not need to change my behaviour".
The old reasoning was "Climate change is not real, therefore, I do not need to change my behaviour"
The new reasoning is "Climate change is real (and unstoppable), therefore, I do not need to change my behaviour as nothing I do will matter."
You will not convince this group to change their behaviour as that is a core belief they are defending, not an outcome.