Do you think it will really impact them significantly? I mean, some areas will become less hospitable, while others will probably improve. Food may become a little bit more expensive because of draughts, but we spend so little on food now that even 50% rise won’t be too terrible. All in all, I don’t see global warming having a dramatic impact on people’s lives, perhaps with the exception of people having to move because of it - but then again, even that’s not huge, as people move all the time.
The biggest risk is probably when a lot of people in a given place will want to move at the same time (and/or into the same destination), as it can cause political instability.
Global warming could end life on earth, or at least cause an ELE where 90%+ of organisms are wiped out. The biggest threat I think is creating a feedback loop where warmth thaws permafrost, permafrost kicks up methane/carbon gases, causing more thawing and faster at that, then it'll get bad really fast.
Politically I think water wars could be big depending on how much water is lost as a result of evaporation and polution, I think this could be more pronounced in Africa and the Middle east, but we could have issues between Mexico, AZ, California and the south western USA where it's more draught ridden. Forest fires will continue to get bigger and more frequent causing a change in ecosystems where forests may turn to baren deserts.
Lack of water also will cause farming to be tougher. I'm hopeful we eventually science the shit out of all this stuff, but then we could get an asteroid the next year that wipes us out anyway, no use really fearing but doesn't hurt to prepare as best we can.