Climate change is serious business. I read heavily about the Scandinavian colonies in Greenland between 986 AD and 1400 AD. There were about 4000 Norwegian/Danish settlers there raising cattle and sheep, growing wheat and barley, there were dozens of bustling villages with churches and a brewery. There was very busy ice-free shipping between Greenland and Denmark that was open at all times of the year, heavy trade in Greenland with especially whale oil being their main export. A graveyard from around 1300 was exhumed, they found the clothes they wore were normal warm weather clothes. This was on the west coast of Greenland around 65 degrees latitude. Nothing on the east coast. The eskimos lived only in northern and northwest Greenland, even as high as the northern tip of Greenland 82 degrees latitude. That's how warm it was.
Around 1400 it got much colder, all the Danish crops started failing due to the cold, and the sea became so full of ice there was no longer any shipping lanes open to Denmark, and the Danish population of Greenland went very low. The eskimos moved down from northern Greenland because of the cold, attacked and took over what was left of the villages.
Now as the ice recedes they are finding stone buildings there 1000 years old.