[whatever230522]

If the average temperature were 0°C there would be no life on earth because all the water would be frozen. No humans, at any rate.

If the average temperature were above 40°C there, again, would be no life on this earth, because proteins start coagulating at about that temperature, weird vent hole creatures at the bottom of the oceans exempted.

A temperature change of 1.5°C is a big change in the context of temperatures that support life, let alone temperatures that allow humans to have the foods and outdoor fun that we’ve enjoyed this past few hundred thousand years.