Irvin Studin, in an article in this morning's Financial Times, argues that two places on earth are the likely loci of conflict: (1) the South China Sea and (2) the Arctic. I'm not so sure about the first; we already have some kind of equilibrium in the South China Sea; the only question is how stable it is during the coming century. Global diplomats are basically starting from square one in trying to establish some kind of regime to avoid armed conflict in the Arctic, the rich resources of which are only just becoming accessible for the first time because of global climate change (see, e.g., here).
The Arctic historically has been treated as res nullius (unowned lands) because of their lack of accessibility. But as Studin points out, as the ice melts and they become accessible, a number of countries, including Russia, Canada, the US, Norway, and Denmark (of which Greenland is a semi-autonomous region), have overlapping and therefore potentially conflicting claims to mineral-rich arctic lands and waters. Thus, res nullius may soon be converted to res publicae (public property, under assertion of sovereignty). One goal of international negotiations is to either prevent that by converting the Arctic instead into res communes (common property), similar to Antarctica or by controlling assertions of sovereignty (res publicae) to avoid potential conflicts.
National security issues are among the most significant secondary effects of climate change. And they have not been lost on the US Department of Defense (DOD), which, next to the EPA, is taking the threats from climate change more seriously than another other agency in the US government (see, e.g., here and here).