■ Capstone · The Full Century
2000 mapped the baseline. 2100 maps the choice.
Assemble the four exposures into a single surface and the century resolves into two futures: one where the overlap shrinks to under 3 billion people, and one where it grows toward 7.6 billion. The difference is made of policy, not fate.
DATA WINDOW 2000–2100+ · BASELINE 2025 · SSP SCENARIOS · UN POPULATION · IPCC AR6
The century in five eras
One hundred years, five distinct regimes of exposure
1.75 billion in extreme poverty; 26 percent without safe water; air pollution already near-universal in Asia's growing cities. The exposure surface is large but unmeasured as a single object.
Poverty falls to 8.5 percent; water access improves; heat exposure climbs to 44 percent. The four curves point in different directions for the last time before climate forcing dominates.
The scenarios diverge. Under low emissions and fast development the overlap begins to shrink; under high emissions it grows. Every tenth of a degree now moves tens of millions of people.
Population nears its peak while the pathways separate by more than 3 billion exposed people. Adaptation built in the 2030s and 2040s is now the difference between coping and collapse at district level.
Committed sea-level rise, locked-in warming, and the habitability of the hottest regions keep moving after the century closes. The 2100 number is a waypoint, not an endpoint.
The surface, assembled
Total person-exposures tell the story the single-hazard numbers hide
A person under three stressors carries three exposures. Counting person-exposures — the sum of the four stacked bands multiplied by population — makes the overlap visible as a single number.
On that metric the present is not a pause. The 2025 surface is larger than the 2000 surface despite twenty-five years of poverty reduction, because heat and air exposure grew faster than poverty and water shrank. After 2050 the pathways separate sharply, and the gap between them is the entire object of this report.
The index
Index the surface to 2000 and the century becomes legible in one glance
Set the 2000 exposure surface to 100. The low-pressure pathway ends the century at 74 — a world materially less exposed than the one the century opened with. The high-pressure pathway ends at 214, more than double the baseline.
The century's first quarter reduced poverty and water exposure faster than any prior generation. The century's remaining three quarters decide whether those gains hold — or get buried under heat.
Pathways
Mitigation sets the ceiling; adaptation sets the floor; both set the number
Four 2100 worlds fit on one chart. No action leaves 7.6 billion people exposed. Mitigation alone, rapid decarbonization without development convergence, cuts the number to 5.2 billion. Adaptation alone, cooling, water, and poverty programs without emissions cuts, reaches 4.4 billion. Both together reach 2.9 billion.
The arithmetic makes the strategy obvious: mitigation and adaptation are not substitutes. They are complements with different jobs. Mitigation removes the exposure that has not happened yet. Adaptation protects people from the exposure already locked in. The polycrisis punishes any plan that funds one and starves the other.
After 2100
The century closes; the exposure does not
Sea-level rise, ice-sheet loss, and the carbon already in the atmosphere keep working after 2100. Coastal exposure continues for centuries; committed warming keeps the hottest regions pushing against habitability limits; the wet-bulb frontier keeps moving poleward.
The 2100+ tail is the reason this atlas treats 2100 as a waypoint. A child born in a coastal city in 2080 will live most of her life after the century's projections end. Her exposure surface is set by decisions made before she is born — and by the infrastructure those decisions did or did not build.
That is the long view. The short view is that the exposure surface responds to the same levers in 2100 that it responds to today: clean air, safe water, poverty reduction, and a cooler climate. None of the four is beyond reach. All four are behind schedule.
Treat every polycrisis exposure number as a co-exposure number, not a single-hazard count. The people breathing bad air are the people standing in the heat on two dollars a day, and any forecast that separates the hazards understates the risk and overstates the time left to act.
Sources & method
What this atlas rests on
All figures are illustrative model estimates, rounded to the precision their sources support.
Historical values calibrate to WHO air-quality and WASH data, the World Bank Poverty and Inequality Platform, the Global Burden of Disease, the Lancet Countdown, UN-Water, and ILO heat-stress accounting. Projections use the IPCC Shared Socioeconomic Pathways — SSP1-2.6, SSP2-4.5, and SSP3-7.0 — as bounding narratives, paired with UN population projections. Where a chart shows one line, it follows SSP2-4.5 and says so.
The combined index weights the four stressors equally and multiplies by population. Alternative weightings would change the level of the index, not the shape of the divergence between pathways.
Read the report as one surface
Start again from the overview, or share the atlas. The four domains are one argument: the overlap is the risk.