We’ve only had 1.3C of global average warming, but it’s enough to popularize the entire category of personal cooling devices. So when people say, “You won’t even notice 1C of global warming,” the market tells us that that’s absolute bullshit.
I can’t imagine they would last long. There is this device my wife used after surgery that runs ice water through a tube to a wrap on her recovering area on and off circulation so its only going 50% of the time. Had a huge resevoir I would empty water from and fill ice into. It was crazy how much ice I had to make and constantly replenish and she was in a comfortable envirnment resting in bed. Can’t image how someone being active and out in the heat with something covering way more body surface area is going to have it last long and they would need to be near a constant source of ice.