I think the Doomsday Clock serves a useful purpose in that it causes people to think about the world's situation a lot more than if no one brought it to our attention.
I'm betting many more folks become active in chaitable, environmental, and philanthropic causes as a result of the annual report on the clock.
It has a kind of a chintzy scare factor to it, but it also is a sort of looming reminder to us that there are issues out there, such as global warming, hunger, and -believe it or not- slavery, and other issues that need to be addressed.
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From 2 Peter 1:10 So, dear brothers and sisters, work hard to prove that you really are among those God has called and chosen. Doing this, you will never stumble or fall away.