If the climate isn't stabilized, farming isn't going to work out (and neither is pastoralism). The unpredictable seasons affect domesticated ecosystems as well as wild ones, that's already starting. Gathering is going to be very tricky too. Overall, these human populations, even if they survive, would have a larger chance of dying due to bad unexpected thing, which looks like extinction over a longer timeline as the isolated populations die out. And if anyone mentions hunting, laugh at them.