Models and scenarios
Models let us explore what could happen when we cannot run the experiment in the real world: how a flood spreads through a city, how a grid behaves in a heatwave, how a price shock moves through food systems. Scenarios set out plausible futures to test against. The Global Centre for Risk and Innovation (GCRI) builds and uses models with attention to validation, assumptions, counterfactuals and uncertainty, and never presents a model output as an observation. This page is part of science and methods.
- 01InstitutionThe Global Centre for Risk and Innovation (GCRI)
- 02Service levelR0: information and enquiries
- 03In briefThe short answer
- 04Four disciplinesWhat every GCRI model must show
- 05CounterfactualsAsking what would have happened otherwise
- 06ScenariosPlausible futures, not predictions
- 07Key termsTerms used on this page
GCRI · Institution · service level R0
The short answer.
Models and scenarios are the tools GCRI uses to explore what could happen when the experiment cannot be run in the real world, such as a flood spreading through a city or a price shock moving through food systems. Every GCRI model shows its validation, assumptions, counterfactual and uncertainty, and a scenario is a plausible future, never a prediction.
Systemic exposure in Indonesia.
Where people and networks concentrate, the exposure through which shocks travel between systems, shown for Indonesia as an example geography for this subject.
What every GCRI model must show.
A model is only as useful as its user's understanding of where it holds. These four elements are published with every model result.
Tested against reality
Compared with observations it was not built on, using uncertainty quantification and model validation.
Stated, not hidden
Every key assumption is written down, with how results change if it is wrong.
Ranges, not single numbers
Results are reported with ranges and the sources of uncertainty that drive them.
Asking what would have happened otherwise.
Many questions about risk and policy are counterfactual: what losses would have occurred without a flood defence, or how a programme changed outcomes. GCRI uses causal inference and impact evaluation to answer them, states the identifying assumptions and reports when the data cannot support an answer.
Plausible futures, not predictions.
- 01
Purpose
Scenarios test decisions against a range of plausible conditions, including severe ones.
- 02
Design
Built with scenario design and stress testing, with drivers and storylines stated.
- 03
Interpretation
Simulated loss or performance is not observed impact, and a scenario carries no probability unless one is estimated and shown.
- 04
Use
Scenario results inform options for competent decision-makers. Analysis is not the decision.
Terms used on this page.
Each term as this page uses it. Where a standard-setting body defines the term, the wording follows that body.
| Term | Definition |
|---|---|
| Scenario | A plausible description of how the future may unfold under stated assumptions, not a prediction. |
| Model validation | Comparing model predictions with independent observations to judge fitness for a stated use. |
| Counterfactual | What would have happened without the intervention or exposure, which every causal estimate approximates. |
| Uncertainty quantification | Characterising and propagating the uncertainties in a model to state confidence in its outputs. |
Systems, reports and related pages.
Scenarios, options and decision analysis run in DSS in Nexus Foundry. Reviewed scenario work is published in the Scenario and Stress-Test series. Shared modelling methods are organized through the Systems Science and Modelling platform, in development. See also risk science.
Model code, data and parameters are recorded so results can be reproduced, within the rights of each source.
Questions and answers.
Why should anyone trust a model?
What is the difference between a forecast and a scenario?
Can I see the model code?
How are model errors corrected?
Does GCRI use AI models?
Around GCRI.
Start with an enquiry.
The current service level is R0: information and enquiries. An enquiry receives a reference and names the next step; applications, payments, compute allocations and registrations open only when their team, terms and review capacity exist.