How should the world respond to North Korea's h-bomb claim?

Aired: 1/6/2016 | 0:08:42 | Clip
Gwen Ifill talks with former Obama administration official Wendy Sherman and Siegfried Hecker, former director of the Los Alamos National Laboratory, about why we should be worried about North Korea’s purported test of a hydrogen bomb, how world powers should respond and possible motivations for Kim Jong Un.