Nevertheless, in the absence of migration, one third of the global population is projected to experience a MAT >29 ☌ currently found in only 0.8% of the Earth’s land surface, mostly concentrated in the Sahara. Populations will not simply track the shifting climate, as adaptation in situ may address some of the challenges, and many other factors affect decisions to migrate. We show that in a business-as-usual climate change scenario, the geographical position of this temperature niche is projected to shift more over the coming 50 y than it has moved since 6000 BP.

Supporting the fundamental nature of this temperature niche, current production of crops and livestock is largely limited to the same conditions, and the same optimum has been found for agricultural and nonagricultural economic output of countries through analyses of year-to-year variation. Here, we demonstrate that for millennia, human populations have resided in the same narrow part of the climatic envelope available on the globe, characterized by a major mode around ∼11 ☌ to 15 ☌ mean annual temperature (MAT).

All species have an environmental niche, and despite technological advances, humans are unlikely to be an exception.

Mortal empires map revealed