it is wednesday, january 6th. it is 5:00 a.m. this is cnn breaking news. breaking overnight, north korea says it exploded a hydrogen bomb. this is the very first time the reclusive regime can made a claim. yes, it did nuclear tests. those were for crude devices. a hydrogen bomb would be a huge escalation and present huge new challenges for the u.s. in terms of security. now, this apparent underground test set off political tremors around the world all night long, prompting an emergency meeting of the united nations s city council. that s set for a few hours from now. joining us for the very latest. cmn will ripley live for us from beijing. this is a big provocation by the north koreans. reporter: absolutely, christine. if their claims are true that if is, in fact an h-bomb, it s a different situation within have you this regime, which invested