The regime in Pyongyang has tested a third nuclear device and the depressing diplomatic ritual has begun again.

The liturgy is familiar: the threat, the ineffective warnings, the big event, the brief uncertainty about what happened, the regime's confirmatory boast, the international outrage, the hand-wringing, the American reassurances to Japan and South Korea, the realisation that only China can apply real pressure, the mild Chinese response, the month-long wait for a slight tightening of UN sanctions, then the tacit acceptance of a new normality in which the world becomes that little bit more resigned to North Korea's weapons, and those capabilities become more technically credible.

But what if this time things turn out differently?

The main factor that would change the North Korean nuclear equation is China. In 2009-10, China seemed to resolve its internal policy debates about North Korea in favour of allowing fairly much any provocation short of war on the peninsula. Hence the disappointing Chinese response to the sinking of the Cheonan, the bombardment of Yeonpyong island and last year's missile tests.

But we should not assume that the internal Chinese debate is settled forever. There have been heartening signs of late that the debate has been reopened and may even be tilting in favour of applying serious pressure to Pyongyang.

Kim Jong Un's decision to test this week is a clear affront to the new Chinese leadership. After all, China had warned the North not to test, with outlets such as the Global Times claiming there would be a 'heavy price' to pay. And the timing of the test around Chinese New Year would have compounded the embarrassment, as Chinese netizens are pointing out. Indeed, the rise of social media and that fact that many patriotic Chinese are so openly critical of North Korea may itself help to shift the Chinese policy debate.

It is frequently argued that Beijing cannot or will not push Pyongyang for fear for contributing to instability and regime collapse. But this is not a matter of all or nothing. It should be quite possible for China to apply graduated pressure, such as temporary restrictions on oil, food or other cross-border commerce, as well as diplomatic signals like suspending or downgrading some official or military visits.

These may seem small and inconsequential steps when compared to the determination of the North Korean regime to possess the world's most dangerous weapons. Still, a shift in China's stance offers the only prospect of movement on this issue. Of course, as some analysts note, this kind of measure could also make North Korea exasperated with China. But where else is Pyongyang going to turn?

Photo by Flickr user Bert van Dijk.