tested the h bomb, but is it true, and what does it mean? our exclusive with the head of the iaea, and the american nuclear scientist with the best view of north korea. plus a year after the "charlie hebdo" attacked, ushered in isis gone global, our exclusive with a cartoonist. >> this past year has been difficult. we had to rebuild the newspaper. we had to rebuild ourselves. confront our pains.

and back to the future, my trip to a nuclear plant back in 2008. good evening, everyone. welcome to the program. we're in london. with that, north korea announced to the world that it successfully tested its most powerful weapon to date. a hydrogen bomb. that's a thermonuclear weapon more powerful than the atomic bomb. the news sent alarm bells all over the globe. the united states, japan, south korea, even pyongyang's long-time ally, china condemned the attack, but the united

states, the white house just said that initial reports are not consistent with a successful h bomb test, and the white house says the international community continues to investigate. now, ahead of a u.n. emergency security council meeting on this issue, the secretary general demanded that kim jong-un cease any further activities. this test still marks a dramatic escalation of north korea's capability. moving rapidly ahead, despite international sanctions. the international atomic agency described the test. last september the general warned that north korea was busy building up one of its nuclear facilities, and he joins me exclusively now live from iae head quarters in vienna. welcome to the program. let me get straight to it. do you believe -- do you think

it's possible that north korea would have tested the hydrogen bomb? >> the international cbtbo is monitoring a nuclear test. it is collected information on seismic events, and they have detected unusual seismic event. however, it is still at an early stage. it'll take more time to have better understanding of the event. >> does the seismic event that you talk about, the tremors, does that match the size of an h bomb test? >> the seismic event was around around the five, and it is similar to that of 2013 when north korea conducted the test, but conducting nuclear weapon test is a clear violation of u.n. security council, and it is

deeply regrettable. >> what is the world to do about this? you head the iaea, neither sanctions seemed to have work for engagement. there was a period of engagement with north korea what was brief. what must be done. >> north korea to fully implement all regulation of security council and iaee. these resolutions expressed serious concerns and called on north korea to refrain from further such tests. iaea is ready to contribute to a peaceful resolution. we have the experience of conducting safeguards in north korea, and our inspectors are ready to go at short notice when requested. >> describe for us the plutonium process which we thought had been paid to and the uranium process that seems to be

gathering a pace. >> the iaea does not have the inspectors on the ground now since april, 2009, but we're monitoring the situation through satellite imagery, and as i stated in september, we've observed the activities like the construction of light water reactors or operation of the five megawatt reactors, or expanding the enrichment facilities. in 2013, north koreans, stated that they will readjust and restart the nuclear activities. all of these combined make me have concerns, and that is why i made the statement in september. >> director general, thank you very much, indeed, for joining us tonight.

thank you so much for joining us from vienna, and now we turn to new mexico where a nuclear scientist has perhaps had the best and most consistent access praking north korea's nuclear program, and he's been warning it's been progressing by leaps and bounds. thank you for joining us. you just heard what the director general said and what the united states has said pouring some skepticism on north korea's claims. from your best analysis, what do you believe happened? >> well, the most important thing is that they fired a successful nuclear test. you know, whether it was a hydrogen bomb or not, of course, is important, but the most important aspect, they had their fourth nuclear test, and with that test, either they've managed to potentially make a hydrogen bomb, or they've been able to manage and make one of

their simple bombs smaller and lighter and, therefore, more threatening. so i don't consider this a failure of a hydrogen bomb. certainly, the explosive magnitude was similar to their third test. and more in the range of sort of hiroshima and nagasaki, but that is plenty, and i consider that test to have been successful. >> you know, you talked about making it smaller and lighter. so, obviously, they're looking for kind of a miniaturization in order to put it on weapons, on ballistic missiles and the like. is that what you're worried about most? >> this test, most likely, was aimed precisely as to how to make them smaller and lighter, and one possibility in doing that is not only to make a smaller and lighter normal atomic bomb, but perhaps to go sort of halfway between an at atomic bomb and a hydrogen bomb. that is what we call a boosted

fishing bomb. in other words, it's one that's, like, turbo charged bomb, and this boosting process actually uses the hydrogen iso topic fuel. it's really not a hydrogen bomb, but it's possible they went in that direction. that would allow them in the end to make the warhead smaller and lighter so they could mount them on a missile. >> so whatever they've done, it's progress from their point of view and from their capacity. you were there a few years ago when they showed you a secret facility for uranium enrichment. you've also been in china talking amongst a whole group of experts about, as you rightly say now, their expanded stockpile. tell us what they have as best you as you or anybody knows. >> so, in 2010 when i was in november, they showed me, and

quite frankly, it was an enormous surprise to see a centrifuge facility that's able to enrich uranium for the second pass to the bomb. what was surprising was the sophistication and the size of that facility, and the best as we know, that's the last time we know that anybody outside of north korea has been in the nuclear complex. the best that we can tell from overhead is that they've continued to expand that complex substantially, and so whereas the plutonium path to the bomb for which you use nuclear reactors, and they have one small reactor that at best can make one bomb a year, having opened up this centrifuge capaci capacity, that perhaps allows them to make as many as six bombs per year. they expanded over the last five years significantly their capacity to increase the size of

the arsenal, and certainly, one thing i've argued for over and over is to try to get them not to test in order that they wouldn't increase the sophistication of that arsenal. >> well, professor hecker, that's the big question, isn't it? how does one -- it doesn't seem that anybody or anything has much influence. as i proposed to the director general, neither sanctions more engagement, and both have been tried over the last ten years or so, under several different u.s. administrations, china doesn't seem to be making much end roads either. what has to happen now? >> well, of course, that's difficult. especially for a scientist to answer. what i have been trying to promote for a number of years by watching how the size and sophistication of the program has changed is the diplomatic route to get north korea, what i

call the three nos, no more bombs, no better bombs, and no more experorts. that has not been sufficient. i think we sat back, the entire world, not just the united states. it's china and the rest of the world. and they've watched north korea go from in 2003 most likely when they built their first bomb, to 2005 and 2008, i said they have a bomb and not a nuclear arse l arsenal. today they have a nuclear arsenal, and by continuing to test, they make the arsenal more threatening. >> thank you for your unique insight, and it's a troubling situation. now we turn to paris. the city of light that spent much of last year cloaked in darkness after multiple terror attacks. it started one year ago at charlie hebdo.

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now, this special anniversary edition of "charlie hebdo" hits french newsstands today. it marks one year since the deadly terror attacks on the offices in paris on the seventh of january, 2015. two gunmen stormed the building and opened fire, killing 12 people. the latest cover depicts god carrying a gun and the cartoon, one year on the asis anyones still at large. it was drawn by reese who survived the attack and sat down exclusively with our jim bitterman to reflect on the nightmare day and to ponder what it means for freedom of speech in the future. >> translator: this past year has been very difficult. we had to rebuild the newspaper. we had to rebuild ourselves. confront our pains. so it is on the one hand, a personal struggle. it was a personal fight. so here we are, one year later, with a vision which might be

even a little more pessimistic today than it was one year ago. >> reporter: is it more difficult to be funny now than before? >> translator: no. we always manage to find the urge to laugh because we have the will to live. to laugh is like going to the restaurant. the it's like going for drinks. it's a pleasure one has to continue to have. we don't have less of an urge to laugh. >> i think you said you're no longer going to do caricatures of muhammad. why is that? >> i didn't say that. i said it was a question of circumstances in that we don't rule out anything. maybe one day again we'll draw muhammad as a matter of principle. >> reporter: how do you put in perspective the attacks and the 13th of november which involved several hundred people? >> translator: i may be wrong, but i'm under the impression that after january 7th, and

maybe even before, the authorities fear third down type -- feared this type of thing could happen. but how you get get the population to understand something before it happened? maybe we had to wait until november 13th to everyone realized such attacks could hit everyone. i get the feeling things were out of sync between what the political powers had understood was going to happen and the population who could not imagine such events could take place. i would say that perhaps since november 13th, it has become easier for the political powers to take measures such as the state of emergency. i don't think a state of emergency would have been accepted before then. >> reporter: you're printing one million copies this week of "charlie hebdo" on the anniversary issue. here's the cover. can you explain what it means? what is it, exactly?

>> translator: it's a caricature representing the symbolic figure of god. to us, it's the very idea of god that may have killed our friends a year ago, so we wanted to widen our vision of things. faith is not always peaceful. maybe we should learn to live with a little less of god. >> reporter: so this is not muhammad? >> translator: no. this is not muhammad. it's above him. it's the god of all believers. >> reporter: thank you very much. >> reese with our jim bitterman in paris. after a break we return to north korea as we imagine a world where the herm it kingdom works with the west to do nukes. it sounds like the stuff of dreams, but not so long ago it was a reality that i witnessed, the north korea that was, next. hwe'll match any competitorse best prprice. this? what about this? price match guarantee. and this? yep! so no monkey business, no tomfoolery? oh, we do have tom foolery, tom.

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and finally tonight, imagine a world where secretive paranoid north korea looked like it was playing ball by eliminating its nuclear threat. that's the north korea that i along with a small hand full of journalists witnessed in 2008. we thought it would be interesting to look back at our trip to the plant in light of what's just happened. >> reporter: we are 60 miles outside the can capital, pyongyang, driving down a long, bumpy road, on the way to a tightly-shutted outpost at the center of worldwide controversy. thank you for having us. we're interested to see what's going on here. this is the top secret nuclear plant where north korea used to make energy and has made plutonium for nuclear weapons. this is the last place we thought the north koreans would

ever let us film, but they want to make a point to cnn and to the world. in february, 2007, north korea agreed to disable this plant in exchange for fuel oil, trade, and being removed from the u.s. list of state sponsors of terrorism. though some might call this a carefully cover yo graphed show, the tour appeared to be a sincere effort to prove they've shut the plant down. on a hillside overlooking the nuclear plant, north korean officials set up a reviewing stand and seats for the u.s. state department delegation and the others who had come to witness the destruction of their

cooling tower. as dignitaries, technical experts and the press waited, an official from the plant gave the signal. first, a warning flair, and three minutes later, a massive cloud of smoke. as the tower crumbled, the sound of the blast finally hit the air. there was a moment of stunned silence as it sank in. then a quiet handshake between the u.s. point man on north korea and the director of safeguards at the nuclear plant. >> a complete demolition. >> reporter: dr. lee said he was sad to see his life's work destroyed, and yet, he said, i hope the explosion of the cooling tower will make a contribution to peace, not only for the korean peninsula but for the whole world. it has taken north korean

experts two weeks to carefully latex ploesi lay the explosives. >> it's not simple to employblop and make it come down. >> reporter: after surveying the rubble, they said the stage is now set for the next phase of negotiations, to fully dismantle this and hand over the plutonium, including the bombs it has produced. >> that was then, and that was it for plutonium processing, but two years later our guest was shown a new secret facility right there for enriching uranium, the other route to the bomb. at the end of last year, north korea fully and officially restarted the facility and it started this new year with a big and ominous bang. that's it for our program tonight. you can always listen to our pod

cast, see us online, and follow me on facebook and twitter. thank you for watching. and good-bye from london. (singing alougetting to know you. getting to know all about you...

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this is "cnn newsroom." we want to welcome our viewers joining us from the u.s., and a warm welcome back to our international viewers. i'm errol barnett. >> and i'm rosemary church. chinese stock markets are shut down trading for the second day this week after sharp losses early i