I would bet you and I evaluate the problem similarly, I think there are remote but plausible scenarios that are almost intolerably bad (and these become likely if we keep polluting).

But there are left-leaning but not scientifically literate people who honestly believe most life on Earth is already doomed.

This obviously leads to despair in their political thinking and personal lives. I’ve even heard of people contemplating suicide.

I don’t think this is warranted given what we know and the uncertainties involved. Humanity still has a future worth living for even in the most frightening scenarios.