Where would like half the earth's population move to, if things happened quick enough for you to experience the results of a new ice age? Like Half or Eurasia and North America would be covered in ice...
The Day After Tomorrow shows Mexico offering refuge to the USA. Shame someone's building a massive wall the length of the border…
You are aware that "The Day After Tomorrow" was a fictional movie, right? It's a dramatisation set in the real world. Fantasy Mexico can do all manner of things.
Icy tundra is the only thing more hostile to life than true desert. You would not believe how quickly you'd be freeze-dried in an ice age...
Literally cool I assume?
I'm going off topic here, but I just want you to know that this is the first time in months, maybe years, I've read the word "literally" used both correctly and not pedantically* and I'm all shaken up by it.
*) (well aware that this comments fails my own criterium)
You may enjoy knowing that the singular of criteria is criterion (Greek, not Latin). A criterium is a bike race, from the same root: a κριτήριον is a decision, with the same nuance of meaning as English judg(e)ment.