No kidding, it is all guesstimates and conjecture.
Ditto with MAN_MADE global warming. Who caused the last global warming which ended the ice age? Cave man?
Actually, the last prolonged global warming period ended around 1380. Life was good while it lasted. The vikings stopped pillaging their neighbors, settled Iceland, Greenland and (even briefly) modern Newfoundland, where they planted grape arbors and made wine for two decades or so until the natives grew too much for them to handle.
They lasted four centuries in Greenland. They even left written and archeology records which indicate at least one dairy farmer had a herd of 3000 head of cattle.