Basically, the growing season is what I was more concerned about...
I am in the northwest, only one county removed from the Canadian border, and we grow all kinds of stuff in our garden. There have been years where an early frost got my maters or another late producer and there are years where we have harvested them for a month. This has all happened over a 10 year period.
On the other hand, this area grows certain crops - apples, cherries, grapes, peppers, cucumbers, pumpkins, sunflowers, rape seed, wheat, and other crops very well. Those are my observations as a hobbyist who was also familiar with gardening in the south.
With modern global commerce it is irrelevant. I can go to my grocery store right now, only a few minutes down the road, and purchase fresh food grown in Mexico, South America, Canada, or Asia. I can purchase meats and seafood harvested only days ago overseas.
The overall abundance of food options has never been greater at any point in human history! The availability of quality nutritious foods has never been greater in human history.
That will not change due to an increase or decrease in temperatures of a few degrees or even ten or twenty degrees as long as we enjoy peace, prosperity, and abundant energy.
In fact, I believe it will become even better as some of the new emerging agricultural methods and technology are simply amazing! I have friends here in a northern climate who grow fresh fruits and vegetables in greenhouses as a hobby.
With cheap and abundant energy (nuclear or whatever new tech comes up) there is very little that cannot be grown efficiently in a greenhouse or on the fruited plains.
Growing season will be confined to very very limited regions and hot houses, if even possible at all.