Crop yields fall precipitously as temperatures rise, this is data for US crop yields over the last century. Interpretation: for every day spent over 30 deg C (86 deg F) crop yields for the season fall by more than a percent.
As the planet warms just 1-2 deg, corn and soy yields fall off a cliff, since the bulk of days (see the distributions below) move across the 30 deg C threshold. And it is very non-linear. I think for this paper a 2 deg C rise corresponds to greater than 50% crop losses.
That means major dislocations in agriculture. Agriculture in the US will have to shift much further north, incurring major relocation costs. In other areas of the world where countries are not as large, it means that entire countries will lose their agricultural capacity.
These damages should be incorporated into our planning models for global development. They aren't right now.
This is real data: