This isn't an academic question. It is an incredibly practical one.
OP is talking about people who spout doomsday predictions.
I once had a debate with someone who was convinced that humans were going extinct in the next century. He wasn't talking about migrations of hundred of millions, deaths of tens of millions, and climate patterns of droughts and floods changing, which are all present in predictions. He really believed that every single human was going to die. There are people who literally speak bullshit doomsday philosophy.
That's not in any way to say that climate change must necessarily lead to thermonuclear war or anything so dramatic as that, but human extinction is a real threat hanging over our heads at all times. It's something worth being worried about.
I find that laughable. Despite how quickly and how chaotically the climate changes, we are not going to go extinct because earth is becoming uninhabitable
Yes some predictions are dire but if they have a one in a million chance of happening (for example) then it doesn't make sense to divert funds that could be better spent on more certain problems.