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What-If

Explore what could change.

Choose a place, a documented issue and one of its documented interventions, then set how far it goes.

ILLUSTRATIVE SCENARIO — NOT A SCIENTIFIC PREDICTION. Built from documented causes, impacts and solutions plus general qualitative patterns. It contains no modelled numbers.

3 · Intervention
PilotScaledTransformative

Adopted across much of the area, with dedicated budgets and enforcement.

Illustrative scenario

What if Shanghai took a scaled approach to “Groundwater controls and artificial recharge”?

Starting point · documented

ClimateSeverity: High
Subsidence, storm surge and sea level rise in Shanghai

A low-lying delta megacity faces compounding risk from typhoons, storm surge, river floods and rising seas.

The intervention · documented

Groundwater controls and artificial recharge

Strict limits on pumping and reinjection of water into aquifers.

Has substantially slowed subsidence rates compared with the mid-twentieth century.

Schematic direction of change

Adaptation reduces exposure and harm, but the underlying hazard continues to be shaped by global greenhouse gas emissions.

Schematic, unitless illustration: relative pressure over time without the intervention compared with the intervention in place. Not based on measured data.NowLonger term →Relative pressure (unitless)
Without the intervention With the interventionSchematic shape only — no data, units or dates.

Causes this could address

  • Historical groundwater extractionPumping compacted sediments beneath the city, lowering ground levels.
  • Delta setting and low elevationSoft, compressible sediments and low elevation increase exposure to water from sea and rivers.

Impacts that could ease

  • Flood risk to dense infrastructureMetro systems, ports and high-value districts are exposed to flooding.
  • Salt intrusion into water supplyLow river flows and high tides can push saltwater up the Yangtze estuary toward water intakes.

Wider reach at higher intensity is an assumption of this illustration.

How change might unfold

  1. Near term

    Early warning and preparedness measures can reduce harm quickly.

  2. Medium term

    Infrastructure and urban design changes reduce exposure as they are built out.

  3. Long term

    Protection must keep pace with a hazard that continues to intensify unless global emissions fall.

Faded stages are less likely to be reached at scaled intensity.

What this would not change

Local action cannot stop global warming; without global emission cuts the baseline pressure keeps rising.

What it depends on

  • Sustained funding and institutional capacity
  • Consistent enforcement and monitoring
  • Local stakeholder support
  • Participation of affected communities

ILLUSTRATIVE SCENARIO — NOT A SCIENTIFIC PREDICTION. Built from documented causes, impacts and solutions plus general qualitative patterns. It contains no modelled numbers.

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