1) Political action will stay under the threshold necessary for real change on human behaviors to realize limits on human-caused warming. We're gonna heat the planet and politicians will remain anti-aligned and selfishly focused on partisan/regional /short-term gains with the support of their votership.
2) As we heat and resources exhaust, some populations are going to wither, some will adapt, and some will attempt to migrate towards cooler regions (the poles). This will cause political strife. As one particular example, draw a line from China's western extent straight north to the pole, and see how what is present-day Russia defends against "the iron will of 1.4B people" who are struggling to live where they are (China already views itself as an Arctic power). Another: USA pushing north beyond the 49th parallel.
3) Population control is topically political suicide in democracies; no one in power will dare broach it in seriousness at a national or multilateral level. Few such people will even give voice to relating resource levels with population levels. Instead, the mitigation strategy will find its loci in migration control and containment (keeping-their-problems-in-their-own-Stans) like we do today with Bangladesh.
I truly hope I'm wrong, but I have a hunch I'm not ..