[AstralStorm]

The most important bit will be food and water safety, parts ever father from equator will be overloaded in terms of food production. Water facilities are not prepared to deal with the magnitude of change and it will be a lot of work to bring them up.

The big problem here is that such preparations ahead of time are not exactly economically viable, and mostly impossible "just in time" as they require systemic changes.

Once these pressures are bad enough, we'll have a big problem.

[beat]

That's assuming there are mass migrations due to lack of food. Why can't they just adjust crops? We keep imagining agriculture as some sort of on-off switch - "We have crops, and then the global warming happens, and suddenly we no longer have crops". It doesn't work that way. We'll see production declines, maybe, but not sudden elimination of entire food supplies. And production declines can be dealt with intelligently - switching crops, altering harvest cycles, etc. Again, in the past century, humanity has handled a quadrupling of the population and wound up with more food surplus and lower food costs than at any point in history. And that's without whatever future the introduction of genetic engineering, internet-of-things, and other modern technologies bring to the table.