An excellent reminder Jancovici makes in his climate presentations, is that the difference between 1950 climate and the last Ice Age is only 4 to 5°C. Obviously

An excellent reminder Jancovici makes in his climate presentations, is that the difference between 1950 climate and the last Ice Age is only 4 to 5°C. Obviously, 8 billion humans wouldn't be able to live in the last Ice Age. A more indirect analogy is body temperature : having your body temperature 2°C above normal is a pretty bad fever; at 4°C, your life is in immediate danger; anything over that you're seriously harmed or dead.