Hot, dry summer in southern England

5.1Assumptions

Scenario SCN-GBR-HDS-01: what is assumed, and what is held constant.

Baseline

the 2026 reference state in this edition

Drivers

a dry winter and spring; a heatwave above 38 °C in July; grassland fires on the urban edge

Analogues

summer 2022¹¹²⁸; 1976 drought

Interventions

none modelled, the specification describes the unmitigated case

Run state

narrative specification; quantified Foundry run scheduled for Q1 2027

5.2The cascade, step by step

1. 1

   CLI → WAT

   low rainfall and heat cut river flows and reservoir levels

   2022

2. 2

   CLI → HLT

   heat deaths and emergency demand rise

   2022¹¹

3. 3

   CLI → BIO

   grassland and heath fires near cities

   2022

4. 4

   CLI → INF

   rail speed restrictions and track failures

   2022

5. 5

   WAT → HLT

   hosepipe bans; river quality falls

   2022

6. 6

   ENE → HLT

   cooling demand meets constrained networks

   ,

5.3The scenario as a table of steps

How the shock in scenario SCN-GBR-HDS-01 would travel through United Kingdom’s coupled systems, step by step, under the assumptions the edition states.

A teaching model of a conditional scenario under the edition’s stated assumptions: not a forecast, not a prediction and not a warning. Sources: United Kingdom 2026, scenario SCN-GBR-HDS-01 (2026); United Kingdom 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. 11UK Health Security Agency (ed.), Heat Mortality Monitoring Report: 2022. UKHSA, London, 2023.back
2. 28Met Office (ed.), “Record high temperatures verified” (40.3 °C at Coningsby, 19 July 2022). Met Office, Exeter, 2022.back