The great demographic divergence
The century's population splits in two: an aging, shrinking Europe and East Asia, and a young, roughly tripling Sub-Saharan Africa. The next two billion people arrive largely in the regions facing the worst heat, water and grid exposure.
Demographics explorer
The century's demography splits in two. Europe and East Asia age and shrink — fewer workers supporting more retirees, with labor shortages and fiscal strain. Sub-Saharan Africa stays young and roughly triples, concentrating the next two billion people in exactly the regions facing the worst heat, water and grid exposure. Where that youth meets jobs, grid and schooling, it is a demographic dividend; where it meets the development trap, it is the century's sharpest pressure.
Demography multiplies every other curve. Africa's growth lands in the hottest, lowest-buffer regions — so population and exposure rise together. Meanwhile aging in the North raises heat-mortality risk (the elderly are most vulnerable) even as it drains the workforce needed to build adaptation. The two divergent curves strain the same global system from opposite ends.
Demography is why exposure and population rise together this century: growth concentrates in hot, low-buffer regions while aging raises heat-mortality risk in the North. See heat exposure, inequality, and the regional outlook.