successful tested a hydrogen bomb. a potential game changer in terms of global power. right now all we know for sure is that it appears there was some kind of test, but not clear what kind of weapon was detonated. while the north says it was a miniaturized version of an h-bomb, south korea's spy agency says the available evidence points to something smaller. officials there say it appears that the bomb released less than t 10 kilotons. "newsweek's" beijing bureau chief melinda lu joins us. what do we know so far? >> reporter: well, we know there was very likely some type of test of a hydrogen or atomic bomb.