I think you're right. The arable land would decrease so drastically the population couldn't be sustained. And things would likely get very nasty as Europeans and North Americans tried to move south.
Give me global warming over global cooling any day.
"And things would likely get very nasty as Europeans and North Americans tried to move south." I'd take my guns and ammo and move into the ice (or, close to it)...maybe my Sa'ami genes would give me an advantage, lol.