Our team brings decades of experience in system dynamics modeling to build simulators that help you explore climate scenarios with clarity and precision. En‑ROADS models global energy, land, and climate systems to evaluate the possibilities of policy and technology solutions, while C‑ROADS focuses on national and regional emissions pathways and their collective global impact.
Below, you’ll find details on how each simulator works and learn what makes them trusted tools for decision-makers, researchers, and educators worldwide.
En‑ROADS (Energy Rapid Overview and Decision Support) is a climate solutions simulator that lets you explore how decisions in energy, economics, and public policy influence global greenhouse gas emissions and future temperature change. Developed by Climate Interactive, the MIT Sloan School of Management, and Ventana Systems, En‑ROADS captures complex science through detailed modeling and is paired with an easy-to-use interface available in over 20 languages to provide a unique platform for people to explore climate scenarios.
En‑ROADS is a global integrated assessment model (IAM) built using system dynamics methods.
Instant insights: Adjust key parameters—such as renewable energy subsidies or carbon pricing—and instantly observe implications for global temperature change, greenhouse gas emissions, energy markets, and more.
Scientific rigor: En‑ROADS’ outputs are compared to historical data and future climate projections from other leading integrated assessment models.
Accessibility: Built for a broad audience, En‑ROADS enables policymakers, educators, and researchers to explore complex climate dynamics without specialized modeling expertise.
En‑ROADS is an integrated assessment model—a collection of interconnected equations that mimic real-world processes. It is built using system dynamics methodology. The model begins in 1990 and simulates the global energy and climate system through 2100, responding immediately when you adjust factors like energy sources, economic growth, and climate policies. Eighteen interconnected submodels track factors like energy flows, the carbon content of biomass and soil, radiative forcing, and thermal expansion of the oceans. One submodel, for example, calculates the investment, construction, operation, and retirement of energy capacity, including fuel extraction, delivery, and electricity generation.
En‑ROADS model structure overview. See the full Technical Reference for equations, parameters, and sources.
En‑ROADS differs from many other integrated assessment models (IAMs) that aim to find the lowest-cost pathway by assuming perfect foresight and optimal allocation of resources. En‑ROADS is instead a simulation model that explores “what-if” scenarios under different policies and assumptions, using behavioral decision rules to reflect how people and organizations actually make choices with limited information. It is also a disequilibrium model: rather than assuming the economy-energy-climate system is always in balance or moves smoothly between equilibria, its behavior emerges from the interactions of feedback loops, information delays, and decision rules within its structure.
Here’s how the model works:
En‑ROADS uses historical data as a starting point. The model uses data from 1990 for the initial variables in its calculations then simulates changes over time to run through 2100.
The initial values are sourced from reputable research institutions and global datasets. For example, the United Nations estimated the global population in 1990 at 5.3 billion, which serves as the starting value for population. Similarly, historical atmospheric concentrations of greenhouse gases, such as carbon dioxide (CO2) and methane (CH4), are initialized using empirical measurements from sources like the National Oceanic and Atmospheric Administration (NOAA) Mauna Loa Observatory.
Equations provide structure and drive the model. En‑ROADS is built using system dynamics, a modeling methodology that is particularly well-suited to capture the feedback loops, time delays, and non-linear interactions that characterize the climate and energy system. The model includes:
While our modeling team writes most equations in En‑ROADS, others are adopted from the work of other research teams. For example, the carbon cycle portion of the model is adapted from established equations created by Goudriaan and Ketner to simulate how carbon moves between the atmosphere, oceans, and terrestrial sinks.
The equations in En‑ROADS are available in the interactive equations viewer located in the Technical Reference. Model files are proprietary, but can be licensed for use.
Key parameters come from the scientific literature. The equations in En‑ROADS sometimes rely on constants—specific numbers from peer-reviewed scientific research—that describe how systems behave. For example, the progress ratio constant reflects how the cost of renewable energy drops by 20% with every doubling of renewable energy capacity. Many of these parameters are adjustable in the model’s “Assumptions” view, allowing users to test different scientific and economic scenarios and account for uncertainties.
En‑ROADS is tested against historical data. En‑ROADS is tested using real-world data from 1990 to the present day. By comparing the model’s outputs—such as energy demand, carbon dioxide levels, and temperature changes—with observed data, we can confirm that the model behaves as expected. Any discrepancies between the simulated and observed data are used to refine the model’s equations and parameter values, ensuring it accurately reflects real-world trends before projecting into the future. These comparisons are detailed on the Model Comparison—History page in the En‑ROADS Technical Reference.
En‑ROADS is benchmarked against other integrated assessment models. En‑ROADS is benchmarked against integrated assessment models (IAMs) used in the Coupled Model Intercomparison Project (CMIP6). While En‑ROADS does not use data from these external models, comparing its outputs with detailed model outputs under aligned assumptions helps verify that En‑ROADS performs as well as other models that are much more detailed. These comparisons are located in the Model Comparison—Future page in the En‑ROADS Technical Reference.
En‑ROADS is a non-linear system of differential equations, using system dynamics methods, and built using the Vensim modeling software. The code is then translated into WebAssembly via SDEverywhere so that it can run in a web browser.
Ongoing development of En‑ROADS is focused on ensuring that En‑ROADS can address important policy questions and make its insights accessible to a wide range of audiences. Updates are released almost every month.
En‑ROADS is an independent model driven by its own equations. External datasets are used for initial conditions and constants, and the model is calibrated against historical data. Its outputs are generated by the internal equations, with default values and bounds for economic, energy, and climate dynamics derived from an extensive review of the literature.
Details on the default values of specific parameters can be found in the En‑ROADS Technical Reference and the slider and graph descriptions within the app, and many of them can be adjusted by the user.
En‑ROADS is the result of years of collaboration between Climate Interactive, MIT Sloan, and Ventana Systems. It evolved from the team’s work on the C‑ROADS Simulator, which examines the long-term impacts of greenhouse gas reductions across regional groups. The model’s roots trace back to the MIT PhD theses of Dr. John Sterman and Dr. Tom Fiddaman. This collaboration continues today, involving additional partners—such as the UMass Lowell Climate Change Initiative—to ensure the model remains rigorous, reliable, and up-to-date.
En‑ROADS is based on the peer-reviewed C‑ROADS simulator and has been used in peer-reviewed research, e.g., Sterman, Siegel, & Rooney-Varga (2018).
Knowledge Base: Access additional FAQs on En‑ROADS including explainers on specific topics included in the model and details about model dynamics.
User Guide: Use this overview of En‑ROADS to learn to navigate the simulator and interpret results.
Technical Reference: Explore the comprehensive guide to the model’s equations, assumptions, and methodologies.
Free Training: Participate in our interactive training program to learn En‑ROADS and explore the dynamics of climate policy.
C‑ROADS is an online simulator that enables users to explore and visualize the long-term effects of greenhouse gas reductions and land use policies on six regional and national groups. It has played a crucial role in assessing the impact of the emission reduction commitments made by countries to the United Nations. These pledges vary in terms of reduction rates and target years, but with C‑ROADS, we can quickly evaluate whether these combined efforts are sufficient to limit global temperature rise to below 2°C. C‑ROADS is freely accessible, providing valuable insights into the steps needed to combat climate change.
C‑ROADS is the predecessor to En‑ROADS and the models share many of the same components, although their focuses are different. More information can be found in the C‑ROADS Technical Reference.
C‑ROADS (Climate Rapid Overview and Decision Support) is a global climate model that simulates the long-term climate impacts of greenhouse gas emissions from different countries and regions. It enables users to test emissions pathways—such as net-zero targets or reductions from specific blocs—and instantly see the effects on global temperature, greenhouse gas concentrations, and sea level rise through 2100.
C‑ROADS focuses on emissions reductions and their climate consequences across countries and regions (China, US, EU, India, Other Developed, Other Developing), rather than modeling detailed energy and economic dynamics. While En‑ROADS lets users explore the drivers of emissions (such as energy mix, carbon pricing, or technological change), C‑ROADS starts with emissions levels and evaluates their physical impacts. Both models use system dynamics modeling and have parallel physical climate model structures that are calibrated to historical data and aligned with peer-reviewed science.
C‑ROADS is a system dynamics model made up of differential equations that simulate how greenhouse gases affect Earth’s climate system over time. It includes major greenhouse gases—CO2 from fossil fuels and land use, methane, nitrous oxide, F-gases, and others—and calculates their influence on atmospheric concentrations, radiative forcing, global mean temperature, and sea level. The model runs through 2100 and updates results in real time based on user inputs.
C‑ROADS enables users to input emissions scenarios for individual countries or regions—such as China, the European Union, or the United States—and immediately see whether the resulting global pathway aligns with goals to limit warming. Its speed and transparency make it especially valuable in settings where informed decisions matter most—such as policy discussions, negotiations, workshops, and classrooms.
C‑ROADS has been used in international climate negotiations, helping policymakers assess the collective impact of national climate commitments. In use since 2008, it was one of the first models developed to add up national pledges and assess global progress on climate change.
In addition, the simulator is widely used in our World Climate Simulation, a role-playing exercise that mimics the dynamics of UN climate negotiations. In the World Climate Simulation, participants step into the shoes of country delegates and negotiate emissions targets, using C‑ROADS to test their agreements in real time. The experience fosters insight, empathy, and a deeper understanding of global equity issues in climate action. The game is freely available in multiple languages and can be run in-person or online.
C‑ROADS was developed by Climate Interactive, the MIT Sloan School of Management, Ventana Systems, and the UMass Lowell Climate Change Initiative. It laid the foundation for the later development of En‑ROADS and remains a trusted tool for exploring the global implications of emissions commitments.
Yes, the model was reviewed by an external scientific review committee, chaired by Dr. Robert Watson, former Chair of the Intergovernmental Panel on Climate Change (IPCC). The reviewers recommended C‑ROADS for widespread use. Read more in this summary of their review.
Knowledge Base: Access our FAQs on C‑ROADS dynamics and model assumptions, explainers on certain topics, or submit a question.
User Guide: Learn to navigate C‑ROADS and interpret results.
Technical Reference: Explore an exhaustive guide detailing the model’s equations, assumptions, and methodologies.
Free Training: Follow our training plan to learn how to run our World Climate Simulation role-playing game.
For further inquiries, visit the Climate Interactive Support Desk.