In the case of Global Warming its happening to slowly for most people to perceive it as threatening. Even though it massively is.

For Nukes thats just a given nowadays, humans have a remarkable ability to adapt to constant threats. Not in the sense of being able to do something against it but to know it exists and not be terrified every single day. So many things can threaten human life that exist around us and yet we do not get scared after some time anymore atleast not constantly. Look at people living in Australia the entire ecosystem is basically a giant threat to anyone living there. Look at people living in earth prone regions of the world. People adapt and keep on living their lives. This is a fundamental human skill.