That's going to be peanuts against the reckoning of having incredibly population-dense places like Bangladesh, etc. mass-displaced. I think it's going to make the 2010s migrant crisis look like peanuts.
Honestly, I think you are going to see mass death and chaos in third world countries. The militaries of the first world countries are going to unite in a “us versus them” mentality and it’ll be bloody. Billions will die and we might hit our emission reduction goals as a result. The first world will be hit hard, but will adapt and limp along (likely under fascism).