I don't buy that, bb (no pun intended).

Say that the alarmists win the attention of the world and everybody spends their wealth on ameliorating the effects of the worst case scenarios with all the inconvenience and hardships that is entailed in that action.

And nothing happens. Science reverses itself and says, Whoops! We were wrong and the earth is going to be fine without any interference from people.

How well would the "power" the alarmists had gained serve them then? They would probably be hanged from the nearest trees.

No. There's a whole lot more to it than that. Think about it some more.