While well taken, and certainly grave, he sounds like another guy who knows nothing about farming. "Nothing will grow at 45"? Just like Global warming, we will simply change what we grow at which latitude. We may have to drop back to oats, rye, and canola in Wisconsin? Okay, with intense focus and breeding wheat is now up to 90bu/ac. And barley, bred less for yield than other factors, already yields nearly 200bu/ac. Sounds like you're going to be growing more barley! Peasants always ate oats and rye because they're more reliable and have better yields. We only grow and eat wheat because we like it better. So we could double our production there without trying?
There are many other factors. Will a disrupted system and variable conditions mean we need local animals to provide low-cost fertilizer and plant a far wider variety of crops so that a few succeed each year? Probably. Well it's your lucky day! Until 1960 that's what everyone on earth did! This massive, mechanized monoculture is inefficient, oil-and-market oriented, and causes boom-busts as well as mass unemployment. It's the enemy of resiliency. So we'd have to employ more people, more hand-work, and less mechanization on smaller farms, a thing we all still know how to do? That sounds easy.
In addition, since our present system trucks most food 1,000 miles and permits consumption of only A-grades, 50% of non-grain food is probably wasted. So with local sales, and permitting B grades, you can double some food availability right there.
Solar minimums cause more clouds and rain. Okay. Do plants not like clouds and rain more than heat and dry? Is gloomy Olympia more lush and productive than Oklahoma? So would we expect more rain in the high plains of Colorado, Wyoming, and Oregon, permitting more of these mass deserts to be productive?
Although a sideline, breeders have continued the extensive seed selection started in the Victorian era. Although small-time right now, the varieties and gene-pool available in seed catalogues and university freezers is unparalleled in history. These can be both bred out and propagated to planetary scale in a just a few years. If what he's saying is true they WILL be scaled up in a few years, long before we get to the deep minimum.
People, we're not doing anything, and yes, that's a choice, for present reasons. But saying we COULD stop production of food if we act like idiots and refuse to change anything even in desperate circumstance is different from saying it's inevitable. We COULD always shut off the coal plants and modern infrastructure that keeps us alive and die in the dark. We're not going to. Neither are we going to try to grow peaches in Canada in an Ice Age.
We can do it all. It only has to be as hard as we want it to be.