The Doomsday clock idea has a lot of respectable people behind it but I've always been unclear how it isn't just a bias-o-meter. Kahneman and others have done

The Doomsday clock idea has a lot of respectable people behind it but I've always been unclear how it isn't just a bias-o-meter. Kahneman and others have done a lot of persuasive work examining how experts are often quite bad at judgement/prediction. How can we be sure the Doomsday Clock actually means anything substantive (as compared to data)?