You assume that climate change is a problem that can be solved with conventional politics. No, it can't. The only thing that can save us is better technology. We'll just crowdfund a campaign for creating a huge solar shade between the Earth and the Sun that will stop climate change. Problem solved, no politics required. It's just people that can make this happen. People applying self-organization principles on a global scale.
And about the Doomsday clock: I think it's a big exaggerated at the moment, but of course even a local nuclear exchange would be a huge problem for the whole world. Anyway, think about Nietzsche who said:
Man is a rope stretched between the animal and the Superman--a rope over an abyss.
A dangerous crossing, a dangerous wayfaring, a dangerous looking-back, a dangerous trembling and halting.