But is Kim's latest stunt just extravagant bluff in response to US and Korean military activity around the Korean Peninsula and strong condemnation from the UN, or is it something we need to take very seriously?
The people of South Korea appear to be not overly vexed, but then have the Terminal High Altitude Defense system -- THAAD --
which could keep them safe, even in the event of a nuclear strike.
Whatever you think of Kim Jong Un -- his motives, his credibility, even his sanity -- it should be noted that, thus far, he has done exactly what he said he would do in relation to his development of weapons. Everything, that is, except yet attack the US.
The international community has appeared somewhat complacent over the North Korea nuclear capabilities hitherto, despite Kim's claims.
Until relatively recently, we believed his nuclear threat was an atomic device and that his missile capability was not an ICBM, but less sophisticated, with a shorter range and only capable of delivering a limited payload.
Now, it is not beyond possibility that he has an atomic bomb capable of yielding 20 kilotons which could be fitted to an ICBM with a range of 4,000 kilometers. This brings Guam, Japan -- and many others -- in range.
It is the "many others" that I am most worried about. Guam, South Korea and Japan have effective missile defense systems. The "others" do not.
North Korea's apparent possession of an atomic bomb was already causing serious concern. But the possibility of it possessing a hydrogen bomb is even more terrifying.
A 20-kiloton atomic bomb would demolish several blocks in a major city. A hydrogen bomb that was physically similar in size could yield 1,000 kilotons and devastate a whole city.
The science and technical capability to produce a workable hydrogen bomb is also significantly more challenging. Nevertheless, on current performance, North Korea could achieve this relatively soon if not prevented by diplomatic or military means.
To put how terrifying this is in context, the Second World War bomb recently found in Germany
was, according to reports, a mere 1.4 tonnes, but required roughly 60,000 people to be evacuated from Frankfurt to ensure their safety.
No paths to ending this crisis appear to be attractive or effective.
Can the international community -- as some have suggested -- accept a nuclear-capable North Korea and rely on mutually assured destruction between the US and North Korea to work as a preventative measure? Even if MAD prevents Kim from striking US allies, that's not the end of the international community's problems.
One should not forget it was the North Koreans, according to the CIA
, who helped the Syrian regime develop its nuclear capability by building an undisclosed nuclear reactor, which was eventually destroyed by Israeli jets in 2007.
One should not forget also, that only recently the Organisation for the Prohibition of Chemical Weapons (OPCW) intercepted two North Korean ships
destined for Syria containing chemical weapons and the wherewithal to make more.
And of course, the North Korean regime still stands accused of having recently used the nerve agent VX to assassinate Kim Jong Nam in Kuala Lumpa. South Korean officials estimate that the North is sitting on between 2,500 and 5,000 tonnes of this deadly weapon.
Whatever the motivation is for Kim Jong Un to have a nuclear capability -- be it credibility on the world stage, or even state expansion -- it cannot be allowed to persist.
For one thing, his ability to give other despots and terrorists WMD leads to the horrific prospect of ISIS acquiring these weapons in return for much-needed hard cash. It's hard to see ISIS having any scruples about such an arrangement -- or indeed using such a weapon in areas that they are currently fighting the US in the Middle East.
There appear to be no good solutions, but if diplomacy fails -- which must be given a good run by all, especially Russia and China -- there must be a plan to destroy this capability militarily for the sake of future generations.
So yes, we need to take this recent development and the threat it represents very seriously indeed. It will not go away on its own.