Well, I fail to see how reducing the amount of coal and petroleum consumed in North America would be fatal to anyone. It might result in a brief recession, but the economy would roar back as it did in the 1980s when conservation and improved efficiency took hold.
As to the unfortunate Norse who were frozen out of Greenland- they would have been fine if they had converted their lifestyle to that of the local Inuit people. In any event, that was then and this is now. It might be nice to have Greenland warmer, but not at the price of having Africa and India hotter than they are already, plus having Bangladesh disappear under the Indian Ocean. A few scientists may argue that global warming will produce as many winners as losers, but most see it as a net loss to human survival.