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A heatwave that meets an ageing, dense and informally housed district

A conditional statement under stated assumptions, never a prediction.

2 min read0 figures0 tables2 notesNR-STRATEGIC-HUMANSYSTEMS-GLOBAL-2026-BASELINE

Contents
  1. ·Edition home
  2. ·Executive summary
  3. 1People and places change together
  4. 2Key findings
  5. 3Systems and sectors at baseline
  6. 4Risks and capability
  7. 5A heatwave that meets an ageing, dense and informally housed district
    1. 5.1 Assumptions
    2. 5.2 The cascade, step by step
    3. 5.3 The scenario as a table of steps
  8. 6Readings from the other desks
  9. 7The 2027 agenda
  10. 8Systems in depth
  11. AMethodology
  12. BData appendix
  13. CReferences and record
  14. ·Complete edition, for print

5.1Assumptions

Scenario SCN-SR11-HEAT-01: what is assumed, and what is held constant.

Baseline
the 2026 reference state in this edition
Drivers
a multi-day heatwave in a dense district with many older residents, informal housing and a partial power loss
Analogues
Europe summer 2022 heat deaths; ageing-related heat mortality trend2116
Interventions
none modelled: the specification describes the unmitigated case
Run state
narrative specification; quantified run scheduled for 2027

5.2The cascade, step by step

  1. 1

    CLI → HLT

    heat raises illness and death among older residents

    2022

  2. 2

    ENE → HLT

    cooling demand rises and a power loss removes cooling and refrigeration

    2022

  3. 3

    HLT → FIN

    hospital and care costs rise while work hours are lost to heat

    2024

  4. 4

    DEV → HLT

    informal housing holds heat and limits access to cooling

    2022

  5. 5

    WAT → HLT

    water supply falls or runs on reserves

    2022

  6. 6

    FIN → INF

    local budgets absorb losses and defer upgrades

    2024

5.3The scenario as a table of steps

How the shock in scenario SCN-SR11-HEAT-01 would travel through Cities, Demography and Human Systems‘s coupled systems, step by step, under the assumptions the edition states.

StepWhat happensSource
01 Climate to healthHeat raises illness and death among older residents. Analogue or source: 2022.Edition SR-11, scenario SCN-SR11-HEAT-01, step 1
02 Energy to healthCooling demand rises and a power loss removes cooling and refrigeration. Analogue or source: 2022.Edition SR-11, scenario SCN-SR11-HEAT-01, step 2
03 Health to financeHospital and care costs rise while work hours are lost to heat. Analogue or source: 2024.Edition SR-11, scenario SCN-SR11-HEAT-01, step 3
04 Development to healthInformal housing holds heat and limits access to cooling. Analogue or source: 2022.Edition SR-11, scenario SCN-SR11-HEAT-01, step 4
05 Water to healthWater supply falls or runs on reserves. Analogue or source: 2022.Edition SR-11, scenario SCN-SR11-HEAT-01, step 5
06 Finance to infrastructureLocal budgets absorb losses and defer upgrades. Analogue or source: 2024.Edition SR-11, scenario SCN-SR11-HEAT-01, step 6

A teaching model of a conditional scenario under the edition’s stated assumptions: not a forecast, not a prediction and not a warning. Sources: Cities, Demography and Human Systems 2026, scenario SCN-SR11-HEAT-01 (2026); Cities, Demography and Human Systems 2026, references (NR-CIT-1) (2026).

Notes

Numbers are the edition’s reference numbers, so a note reads the same in every chapter. The full list, with every source and its licence, is in Annex C. Annex C, references

  1. 21WHO (ed.), Climate change, heat and health, fact sheet (page dated 31 July 2026; 489,000 heat-related deaths a year in 2000 to 2019, 45 per cent in Asia; over-65 mortality up about 85 per cent from 2000 to 2004 to 2017 to 2021). World Health Organization, Geneva. Observation year 2019. Accessed 2026-11-03.back
  2. 16WHO (ed.), news release on the 2025 report of the Lancet Countdown on health and climate change, 29 October 2025 (about 546,000 heat-related deaths a year; up 23 per cent since the 1990s; USD 261 billion cost among older adults). World Health Organization, Geneva. Observation year 2024. Accessed 2026-11-03.back

Cite this chapter

Valadbaygi, S. (Ed.). (2026). Chapter 5: A heatwave that meets an ageing, dense and informally housed district. In Strategic Systems Report 2026: Cities, Demography and Human Systems (Baseline Edition 2026, Report No. NR-STRATEGIC-HUMANSYSTEMS-GLOBAL-2026-BASELINE) [Draft under review]. The Global Centre for Risk and Innovation (GCRI).

Every citation form of the whole report, BibTeX and RIS included, is on the edition home. Cite this report

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Sector signature

The sectors behind Cities, Demography and Human Systems.

A reading aid: the sectors the findings run through and how strongly they depend on each other.

Select corners · hover lines6 / 15 relations

Context

Heatwave

Cooling demand peaks the grid while rivers warm; heat stress fills hospitals and wilts crops.

W · E · I · F · H · B

Sectors
4 of 6
Relations
6 of 15
Coupling
0.43 share of total

Strongest relations in play

  • Water → Energy · cooling water and hydropower0.6
  • Water → Food · irrigation0.8
  • Food → Health · nutrition0.7
  • Water → Health · drinking water and sanitation0.7
Teaching values for a typical city-region, not measurements for any place. Coupling is the summed strength of the relations in play, as a share of all fifteen.
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