If North Korea has tested a nuclear weapon, as it has claimed, does it matter much that the bomb apparently exploded with a power of roughly half a kiloton of TNT, rather than the expected twenty kilotons? I’m frankly amazed at how many folks in the blogosphere (and commenting in the media) have been answering this with an emphatic yes.

The most significant effect of a test is political. It shows that Pyongyang is willing to defy strong warnings, even from China, and is determined to keep its nuclear arsenal, both of which will have important ramifications in the region (see Japan, South Korea) and beyond (see Iran). The yield of the nuclear device doesn’t change those signals a whit.

The actual performance of the weapon is far less important. A five-hundred-ton bomb is not, in contrast with many headlines, a dud, at least by any sensible definition of that word. (A bomb of that size detonated in midtown Manhattan would kill tens of thousands of people.) North Korea should not, as others say, be quaking in its boots – has anyone altered their views of regime change or the wisdom of military action? Meanwhile some seem to think that the yield of the bomb should influence the response of the countries involved – but quite predictably and reasonably, it has not. This last post, from a widely read blogger, is really peculiar – apparently even a five kiloton bomb is essentially useless, since the United States has much bigger ones. Huh?

A low yield, of course, is not entirely unimportant. It almost certainly would reflect technical immaturity on the North Korean part, which would confirm for many that North Korea is incapable of launching a nuclear-tipped missile. But that wouldn't be news -- and we’re still not going to change our basic judgment that North Korea has the bomb.