Certain crops will become untenable in some areas, but in other areas, certain crops will become tenable that once weren't.

But none of this is new, what's new (aside from the anthropogenic cause) is that Homo sapiens' usual coping mechanism of migration is no longer feasible.

This is where the problems and conflicts will come.

No, more extreme fluctuations (that on average end up being warmer) do not make crops tenable in areas where they previously were not.

Climate change doesn't mean just the temperature become a few degrees warmer. The most noticeable change is that one in century event may happen annually now: extreme heat, extreme cold, floods, hurricanes, etc.

> Homo sapiens' usual coping mechanism of migration is no longer feasible.

Migration is extremely common, that most migrants do not reach Europe or the USA did not mean that they are not migrating.

I may assume that you mean that Europe/USA cannot be the destination of all of them. But, I do not even think that most people is so willing to change to a different place. They will migrate as much as needed but not more.

Sorry, I was implying "large-scale" migration as a mechanism for coping with climate change[0]. That's not really possible without massive armed conflicts in these days of nation states.

[0] https://en.wikipedia.org/wiki/Bond_event

And that is the coping mechanism for overpopulation.