Oh, yeah, like even if it's survivable for humanity in general, it's going to kill billions of humans.

It’s not just about time to increase production. A lot of crops that grow at lower latitudes won’t have enough time to mature in the short summers of higher latitudes and may suffer from weaker sunlight due to the lower angle resulting in more intervening atmosphere. We might eventually be able to breed or genetically modify crops to be hardier — but the former takes time and the latter requires sufficient remaining civilization and security to support the labs.

No doubt the transition period would likely involve more death than most catastrophes in history. In part because there are simply more people. Available sunlight is also less nearer the poles, which already affects agriculture in places like Greenland. Crops would shift. We'd be more dependent on energy and supplemental light for certain crops. Adjustment would be difficult. But quite a bit of land would still be habitable.

Certain investment firms purchased cold-weather ports which were iced in 8 months a year, 20 years ago, which now operate nearly year-round.

> Remember when Trump almost invaded Greenland?

That one may not be out of the woods yet.

You need high oxygen content in the air though. Insect style circulatory systems aren't efficient enough to get oxygen to the cells without the air having a super high concentration of oxygen to begin with.

Basically like how when people can't breath good you put them on oxygen to keep them alive only getting oxygen into the blood is the bottleneck rather than into the body.