Raising the temperature towards what end? If the trend of raising temperatures continue, it will eventually lead to a shooting war, unless the tension is defused somewhere along the way.
The aim of American policy, and that of the GNP, in the long run, is regime collapse. This is the aim of similar policies applied by the US in quite a few cases: Iran, Sudan, Cuba, for example. Yes, THERE IS A POINT in raising the temperature, and as I pointed out before, the DPRK can do little about it, other than "strengthen its deterrent". However, if this had been attributed to some sort of accident, or even left as a mystery, there would be nothing to "defuse", and nothing for ROK to answer.
Anyway, the UNSC is not the only "answer" by the ROK/US. There are also announced drills, and there is the single most important thing pointed to by SampanViking in post 385:
The United States and South Korea have agreed to delay until December 2015 the transfer of wartime operational control of troops on the Korean peninsula to South Korea, the two nations’ presidents announced following a June 26 meeting in Toronto.
In case you missed my point earlier, I think that's the main thing that made the NK torpedo explanation desireable to the ROK government.
Now, on the "sunshine policy", you seem to miss my point. You are, I think, referring to a decades long string of events here, to show that this policy is wrong, when the sunshine policy was in place for a few years only.
There were several assasination attempts by DPRK agents against RoK presidents (especially when they were travelling overseas). Infiltration and sabotage, plane bombing, naval skirmishes, kidnaps, border shootings (even of tourists), etc.
But if indeed, both sides did not end their belligerence, how can this be used to prove that the GNP is right and the DP is wrong?
It is more interesting to look at the big picture, which the same post by SampanViking brings out. South Korea and Japan are both going through rather 'heavy' internal political contention, and of course, Taiwan too. The reason is basically the same one in all three cases: the rise of China is posing serious questions of adjusting for the three states. In all three cases, the issue is how to balance the US and China. Note also that significantly, another "use" of the Cheonan incident was the resolution of the Japan basing problem in favor of the US.
For the GNP, the answer is to tighten the alliance with the US. The GNP's policy in this crisis, as well as before and after, serves this purpose. For the DP the answer is gradually to shift towards China while pushing the US off a bit, so that you end up with some sort of equidistant relationship. The "sunshine" policy, as well as the wish to end the special military relationship with the US, both serve this end.