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World3 Simulator — What happens to civilization by 2100?

In 1972, a team of researchers at MIT built World3 — a computer model that simulates how population, industrial output, food production, pollution, and natural resources interact over time. Their findings, published in The Limits to Growth, showed that business-as-usual leads to overshoot and decline.

This tool lets you explore those scenarios yourself. Pick a preset to see what happens under different assumptions about technology, policy, and resources — or tweak individual parameters in the Advanced editor.

Start exploring How does the model work?

What Can You Do With This Simulator?

Unlike static explanations, this World3 simulator lets you experience the Limits to Growth model interactively. Run simulations from 1900 to 2100. Explore collapse scenarios, test optimistic technology assumptions, or see how comprehensive policy changes can avoid overshoot. Adjust individual model constants and watch the system respond in real time.

Choose a scenario

Explore with your favorite AI

Copy any of the prompts below into ChatGPT, Claude, or any AI assistant. The AI can call the World3 API at limits.world to run simulations and answer your questions.

What if we halved birth rates?

Use the World3 simulator API at https://limits.world (see /llm.txt for instructions). What would happen to world population, life expectancy, and resources if global birth rates dropped to half their current level starting in 2026? Compare with the standard business-as-usual scenario.

What if we doubled resource efficiency?

Use the World3 simulator API at https://limits.world (see /llm.txt for instructions). What would happen if resource extraction efficiency doubled and pollution was cut in half through technology, starting from 2026? Show me population, industrial output, and pollution trends compared to business as usual.

Create your own scenario

Use the World3 simulator API at https://limits.world (see /llm.txt for instructions). I want to explore a custom scenario: [describe your what-if question here]. Run the simulation and explain what happens to civilization by 2100.

Go Deeper

    The Story Behind the Model

    From a controversial 1972 report to the planetary boundaries framework — how The Limits to Growth shaped our understanding of global sustainability.

    How does the model work? Explore scenarios

    Common Misconceptions

    The Limits to Growth has been widely misquoted and misunderstood since 1972. Here are the most common objections — and what the model actually says.

    History Explore scenarios

    How does the World3 model work?

    In 1972, researchers built a computer model of civilization's trajectory. It tracks five things: people, industrial output, food, pollution, and natural resources. Below, we walk through the big questions it answers — and show you exactly what it assumes.

    Explore scenarios Edit constants

    Compare scenarios

    or
    Edit constants Calibrate from data

    Advanced: edit constants

    Adjust any of the World3 model constants below. The simulation updates automatically as you change values. Each constant controls a specific aspect of the model.

    Calibrate from data

    What Is the World3 Model?

    Try the simulator → History Model

    The Limits to Growth: Understanding the Book That Changed Everything

    Try the simulator → FAQ History

    World3 Scenarios: Collapse, Technology, and Sustainable Paths

    Try the simulator → FAQ History

    API & Developer Resources

    Use the World3 simulator programmatically. Run simulations, retrieve presets, and integrate with AI agents.

    Endpoints

    Method Path Description
    POST /api/simulate Run a World3 simulation with custom parameters
    GET /api/presets List presets, constants, and variable metadata

    Quick start

    Run a standard simulation with a single request:

    curl -X POST https://limits.world/api/simulate \
  -H "Content-Type: application/json" \
  -d '{}'

    Use a preset with custom overrides:

    curl -X POST https://limits.world/api/simulate \
  -H "Content-Type: application/json" \
  -d '{"preset":"comprehensive-policy","year_max":2200}'

    Specifications & discovery

    Resource URL Purpose
    OpenAPI spec /openapi.json Full API schema (OpenAPI 3.0)
    Agent manifest /agent.json Machine-readable capabilities for AI agents
    Source code github.com/serroba/world3 Spec files live at app/openapi.json and app/agent.json

    Response shape

    POST /api/simulate returns:

    {
  "year_min": 1900,
  "year_max": 2100,
  "dt": 0.5,
  "time": [1900, 1900.5, 1901, ...],
  "constants_used": { "nri": 1e12, ... },
  "series": {
    "pop": { "name": "pop", "values": [1.6e9, ...] },
    "nrfr": { "name": "nrfr", "values": [1.0, ...] },
    ...
  }
}
    Interactive API reference Explore scenarios OpenAPI spec Agent manifest

    Calibrate & Validate

    Calibrate model constants and validate simulation output against real-world observations from Our World in Data (OWID).

    Calibrate constants from OWID

    Fetches observed data from Our World in Data for the chosen entity and reference year, then fits World3 model constants to match the real-world observations. The table below shows which OWID indicator was used for each constant and how confident the mapping is.

    Validate against OWID observations

    Runs a default World3 simulation and compares each output variable against the corresponding OWID time series. The metrics table shows how well the simulation tracks observed data (RMSE, MAPE, correlation) and which OWID indicator each variable is compared against.

    Explore scenarios Compare scenarios