The Economist has a good leader (and an extended article) about the biggest possible catastrophe on the horizon. Sample:

The most serious danger is not that one side will suddenly try to devastate the other. It is that both sides will miscalculate, and that a spiral of escalation will lead to a catastrophe that no one wants. Our briefing this week lays out, step by step, one way that America and North Korea might blunder into a nuclear war (see article). It also lists some of the likely consequences. These include: for North Korea, the destruction of its regime and the death of hundreds of thousands of people. For South Korea, the destruction of Seoul, a city of 10m within easy range of 1,000 of the North’s conventional artillery pieces. For America, the possibility of a nuclear attack on one of its garrisons in East Asia, or even on an American city. And don’t forget the danger of an armed confrontation between America and China, the North’s neighbour and grudging ally. It seems distasteful to mention the economic effects of another Korean war, but they would of course be awful, too.

The linked article is an imaginative — and sobering — scenario on how the worst could happen.