First, it’s going to be a bigger change than those periods. The “business as usual” scenario is warmer than today by the degree to which today is warmer than the ice ages. (And I think at least some of those were local climate changes, not global ones?)

Second, it’s not about life everywhere except for people who stop as soon as they finish the headlines. Some farmland will go from marginal to good, others from good to marginal. Unfortunately the latter is going to hurt more than the former will help, fortunately there are already solutions, unfortunately they are expensive. Probably more expensive than green subsidies, even if the tech never improves.

Thirdly, IIRC, we don’t yet know the conditions which would interfere with the thermohaline circulation, but we have observed the bit near the the U.K. — the Gulf Stream — moving north. Mess that up and the U.K. suddenly turns from a pleasant mild-ish climate all year round into something more like Newfoundland, which is at the same latitude.