Primer - What you will explore
Why do we model climate futures?
To limit the negative impacts and consequences of climate change, countries committed in the Paris Agreement to limit climate change to well below 2°C, aiming for 1.5°C.
To understand how to get there – which technologies to scale, how fast emissions must fall, what trade-offs could arise – scientists build climate mitigation scenarios.
A scenario is not a prediction. It is a self-consistent, plausible description of how the world could evolve if certain choices were made and certain conditions hold. Think of scenarios as maps of possible futures. A cartographer does not predict which path a traveler will take; she draws the terrain so the traveler can make an informed choice. Modelers do the same: they map the landscape of consequences so that decision-makers can navigate it with open eyes.
The mapping is done using computation frameworks that link energy systems, land use and economies. By collecting many simulations from these models the Scenario Compass dataset provides not one map, but an entire atlas – a scenario ensemble.
The Scenario Compass is a tool for reading that atlas. It does not tell you which scenario will happen. It helps you to understand what scenarios are available, which scenarios are more feasible and sustainable than others, and what those scenarios tell us about the future.
The current scenario landscape
The Scenario Compass dataset builds on the AR6 scenario database, assembled for the Sixth Assessment Report of the Intergovernmental Panel on Climate Change (IPCC), published in 2022. Since then, new scenarios have extended coverage into areas which the original ensemble left unexplored and include scenarios that better represent current developments and near-term policy constraints, providing a stronger basis for decision-making.
The Scenario Compass database is what scientists call an 'ensemble of opportunity'. This means it contains the scenarios that modelling teams chose to submit – not a systematically representative sample of all possible futures. Some technological and socio-economic assumptions appear more often simply because they were conventional at the time, or because they were the focus of research. The database is rich, but it is not a balanced survey.
Figure 1 · The Scenario Map
Scenario count reflects modelling conventions, not real-world likelihood — more is not more probable.
Feasibility and sustainability
Not every path on a map is equally passable. A route that crosses a lake may be geometrically direct but physically impassable. A scenario that reaches net zero by 2050 – but does so by deploying vast amounts of carbon dioxide removal (CDR) may be mathematically consistent but would require extraordinary technological advance and growth in land use, water demand, energy input, and financing, all simultaneously, within less than 25 years. This scenario is internally consistent – the numbers add up – but internal consistency is not the only requirement for a scenario to be used in decision making.
The Scenario Compass uses two distinct lenses to assess scenarios:
asks: can this happen? It examines whether a scenario's requirement, for example the pace of technology development, fall within the bounds of what is plausible given current knowledge.
asks: should this happen, given planetary and social limits? It examines whether a scenario stays within ecological boundaries and respects basic social thresholds. A scenario that addresses the climate challenge by converting vast areas of natural forest to bioenergy plantations might be technically feasible, yet deeply problematic considering other environmental and societal implications.
These two dimensions are independent. A scenario can be technically feasible but ecologically unsustainable. A scenario can respect ecological limits but assume technological capacities that do not currently exist. Both dimensions matter. Neither collapses into the other.
These assessments are made by an expert panel convened by the Scenario Compass. They are reviewed annually and subject to public consultation. This process matters for a specific reason: these are expert judgments, not objective facts. Scientists can and do disagree about where the lines fall. Rather than resolving this disagreement artificially, the Scenario Compass puts the choice in your hands – informed by expert assessments, you can select your own thresholds and explore how the results change.
Figure 2 · Pathway Explorer
Each line represents one scenario's projection over time for the selected variable.
Checkpoint
Before exploring how these assessments affect benchmarks, a quick check: What is the difference between a feasibility flag and a sustainability flag?
How feasibility and sustainability constraints reshape what 1.5°C requires
You have mapped the terrain and identified which routes are passable. Now: what do the passable routes have in common? What waypoints do they all pass through?
When you filter the scenario ensemble to keep only those that both limit warming to 1.5°C and meet certain feasibility or sustainability thresholds, the benchmark ranges change.
Exposing those shifts is the purpose of Figure 3.
Three findings emerge consistently:
- Considering sustainability and feasibility increases short-term ambition.
- Speculative carbon removal (CDR) reliance is significantly reduced.
- Demand-side transformations become essential for 1.5°C compatibility.