Dashboard Experimental
Human Exposure to the Climate–Pollution Polycrisis
Compound exposure to air pollution, extreme heat and flood risk across the 21st century — three scenarios, 2000–2100
Interactive model projecting human exposure to air pollution, extreme heat and flood risk from 2000 to 2100 under three scenarios, with compound-hazard overlap by world region.
Overview
Climate change and air pollution are usually measured as separate problems with separate policy regimes. In reality, they strike the same bodies, in the same places, at the same time. The climate–pollution polycrisis is the overlap: the populations that breathe PM₂.₅ from fossil combustion are disproportionately the same populations exposed to extreme heat and flood risk, and the compounding of hazards — not any single curve — is what drives health, migration and economic stress this century.
This dashboard projects four exposure pathways under three scenarios from 2000 to 2100: annual mean PM₂.₅ above 35 µg/m³ (WHO Interim Target-1), 30 or more dangerous-heat days per year, residence in the 100-year flood zone, and compound exposure to two or more hazards simultaneously. Use the scenario buttons and the year slider to interrogate the model; the mortality panel decomposes the annual attributable burden by pathway.
How to read the dashboard
Scenario selection controls every panel. Rapid decarbonisation follows an SSP1-2.6 world where the energy transition also removes the dominant source of ambient particulate matter. Middle of the road follows SSP2-4.5, and High pollution follows an SSP3-7.0 world of regional rivalry, continued coal reliance and weak air-quality governance. The year slider moves every KPI card, chart highlight and the regional table in lockstep; press Play to sweep the century.
The headline metric is compound exposure — the population facing two or more simultaneous hazards. It is the most policy-relevant number on the page because it marks where adaptation must be multi-hazard by design.
In a high-pollution future, the population facing two or more simultaneous climate–pollution hazards rises from roughly 0.95 billion in 2000 to 4.9 billion by 2100 — nearly half of humanity. In a rapid-decarbonisation future it falls back below 0.9 billion. The difference is not marginal: it is the distance between a manageable century and a polycrisis century.
Key findings
Decarbonisation is de-pollution. The same transition that phases out unabated coal removes the largest single source of ambient PM₂.₅. Air-pollution exposure falls from roughly 4.3 billion people today to about 0.9 billion by 2100 in the rapid-decarbonisation scenario — while it rises toward 5.8 billion in the high-pollution scenario.
Heat is the fastest-growing hazard. Even under rapid decarbonisation, extreme-heat exposure roughly triples from 0.35 billion to about 1.1 billion people by 2100 because of committed warming. Under high pollution it reaches 5 billion, making heat the dominant driver of compound exposure in the second half of the century.
The burden is geographically concentrated. South Asia, East Asia & Pacific and Sub-Saharan Africa carry the largest shares of compound exposure across every scenario and year. These are the regions with the thinnest adaptive capacity and the least insured exposure, which turns a physical-hazard metric into a development-finance metric.
Method and sources
Projections come from the H Heuristics Polycrisis Exposure Model v1.0, a reduced-form cohort model anchored to published 2000–2020 benchmarks and extrapolated along SSP narratives. Hazard definitions: annual mean PM₂.₅ above 35 µg/m³; 30 or more days per year with dangerous heat (40°C-equivalent or wet-bulb threshold); residence in the 100-year coastal or riverine flood zone. Compound exposure counts people facing two or more hazards simultaneously. Population shares use the UN World Population Prospects medium variant.
Status: experimental. Scenario curves are illustrative model estimates designed for systems reasoning, scenario comparison and magnitude intuition — not point forecasts. Benchmarks are drawn from the sources below; interpolation between them is the model's own synthesis.
References
- [1]WHO. (2021). WHO Global Air Quality Guidelines: Particulate Matter (PM₂.₅ and PM₁₀), Ozone, Nitrogen Dioxide, Sulfur Dioxide and Carbon Monoxide. World Health Organization, Geneva.
- [2]IPCC. (2023). Climate Change 2023: Synthesis Report — Contribution of Working Groups I, II and III to the Sixth Assessment Report. Intergovernmental Panel on Climate Change, Geneva.
- [3]Clement, V., Rigaud, K. K., de Sherbinin, A., et al. (2021). Groundswell Part 2: Acting on Internal Climate Migration. World Bank, Washington, DC.
- [4]Carleton, T., Jina, A., Delgado, M., et al. (2022). Valuing the global mortality consequences of climate change accounting for adaptation costs and benefits. Quarterly Journal of Economics, 137(4), 2037–2105.
- [5]UN DESA. (2024). World Population Prospects 2024: Summary of Results. United Nations Department of Economic and Social Affairs, New York.
Topics
Published open access under CC BY 4.0.
How to cite
APA
Hughes, H. (2026). Human Exposure to the Climate–Pollution Polycrisis: Compound exposure to air pollution, extreme heat and flood risk across the 21st century — three scenarios, 2000–2100 (Interactive dashboard No. HX-2026-006). H Heuristics. https://projects.hheuristics.com/dashboards/human-exposure-climate-pollution-polycrisis/
BibTeX
@techreport{hughes2026humanexposure,
author = {Hunter Hughes},
title = {{Human Exposure to the Climate–Pollution Polycrisis: Compound exposure to air pollution, extreme heat and flood risk across the 21st century — three scenarios, 2000–2100}},
institution = {H Heuristics},
number = {HX-2026-006},
type = {Interactive dashboard},
year = {2026},
url = {https://projects.hheuristics.com/dashboards/human-exposure-climate-pollution-polycrisis/},
note = {Open access, CC BY 4.0}
}