I'm an economist by training, so I'm intimately familiar with models and with people who place absolute certainty in models that end up being spectacularly wrong.
I assume you are in agronomy. Now, I'm not a trained agronomist, but I am very interested in my garden and have a lifelong familiarity with growing things.
I have to ask you a question about changing what food you grow in Iowa: Do you know the size of the plant hardiness zones? How many things does Iowa grow that can only survive in 5a and will wither from the heat of 6a? (Incidentally, I'm fairly certain that much a change in temperature is actually outside of even the median of the mostly wrong models.)
Sorry, I was referring to the a chart that shows global temps from the past 100 years or longer. Something as big as the global climate and how varied it is, really hard to get an exact model to predict the future. You can build models that product many trend lines, but picking what trend is actually going to happen is near impossible until you move closer to an event, kind of like hurricane models.
Growing zones is not so much of a food plant withering in heat, but can it survive the winter temps, think more on perennial plants here. there are a few plants that will not do well in warmer temps, like rhubarb and some blueberries, so you're not wrong. Apples need so many days of cold weather dormancy too, why you don't find much fruit bearing apples south of Memphis, TN.
More with a rising low temps, places like Iowa are going to have a longer growing season. Need to think in terms of growing degree days and not hardiness zones for annual crops.
https://en.wikipedia.org/wiki/Growing_degree-dayGrowing degree days is not a new thing, it is how many grass type crops, like corn and wheat varieties are picked for a certain area.
No, I don't think all of Iowa will ever become hardiness zone 6, but the southern bottom counties may in time. I grew up in SE IA, we can grow apricots there and harvest a crop about 9 out ten years. Late frost at blossom set is what happens for the 2 out of ten years. Where I live now near the Minnesota border, maybe 1 out of 10 years I would get a apricot harvest. Tree would survive just fine, except for those 1 out of 25 years like this winter where the actual temp drops below -25F for a few days and kills the apricot tree (cold snaps the vascular tissue in the stem). Going to be a lot of zone 4 peach trees dead this year in north Iowa/southern Minnesota.
But adjustments that are being made is something like picking a corn variety with a few more growing degree days to maturity to protect existing yield. More CO2 means more CO2 for early weeds that emerge as soon as the soil warms in the spring, higher low temps mean more growing degree days for weeds to grow. More CO2, more carbon for the crop, grow taller faster, needs more nutrient inputs. Slightly warmer winter temps means more insects over winter, etc. Just a slight increase changes lots of variables.
Growing a home garden is easy to control, try basing your living on a few thousand acres of corn and soybeans where it is currently hard to break even, let alone make a profit. Having to spend an extra $10-30 an acre for fertilizer or herbicide might take any profit away or make you go into the hole.