Why yet another model ?

CCEM has two main motivations:

CCEM is a System Dynamics model which presents many similarities with MIT's LimitsToGrowth and its many successors (Herrington, 2022), but with specific focuses:

• CCEM energy production, consumption and transition (from one source of primary energy to another) is more sophisticated than most similar models. This allows for a more precise computation of energy consumption, energy savings, energy sobriety and most of all, the speed of electrification and deployments of renewable energies capacities. This makes CCEM an adequate framework for evaluating policies, such as the policies presented at COP28 and derived from IRENA scenarios.

• CCEM has a richer-than-most model for global warming consequences (damages) and reactions (redirection). CCEM maps out the tangible and human impacts of climate change, such as natural disasters and psychological trauma, and considers the subsequent societal and political responses. These responses may include a reduction in productive capacity due to direct damage or societal costs, and the model anticipates potential political upheavals leading to "pain-induced" decisions.

• CCEM makes the “known unknowns”, which we could characterize as beliefs, explicit. We recognize that, besides the model that translates CO2 into warming provided by IPCC, there are many unknowns that impact both the input (to CO2 emissions) or the “outputs” (consequences of warming). This makes CCEM a suitable framework to reproduce very different visions and trajectories, as we shall see in Section 5.2.

Ecological Redirection

We borrow the term “redirection” from (Bruno Latour, 2017) and many research scientists who work on the Anthropocene (Bonneuil, 2013) (Adeney Thomas 2020). There are two key insights with the concept of redirection: first, there is no roadmap nor any “transition”, the complex system energy/economy/climate/society will evolve in a chaotic manner, demonstrating amplifications and bifurcations that makes forecasting and planning hazardous. Second, the system will evolve through redirections: decisions taken at a given moment in a given context, for instance following a major natural disaster.


The feedback loops that are implemented with CCEM can be summarized in the following figure. The various natural disasters create in parallel a production feedback loop and a societal feedback loop. The first loop is directly related to the fifth unknown of the previous section: what is, eventually, the GDP loss that is the consequence of fires, floods, droughts and canicules? Although this is a difficult topic to investigate, there is a fair amount of literature, as referenced in (Wallace-Wells 2019), to put forward some order of magnitudes. The second loop is the “redirection loop”, where the pain caused by global warming pushes some of the redirection mechanisms.


We introduce a “pain factor” that is fed by the different negative outcomes of global warming and acts as a non-linear trigger to redirection. In the current version of our M5 model, the “pain” is the sum of from three components:


·       Pain from warming: this is the pain cause by being exposed to, directly or indirectly, or the fear of natural disasters and the destruction of lives and properties that they imply.

·       Pain from economic results: we live in a world of growing inequality; the social balance requires growth and some form of redistribution. As growth declines (even more if it becomes negative), governments have a hard time to manage the “discomforts” of a growing part of their population.

·       Pain from energy shortages: as energy price go up, people and companies have to reduce their usage, up to the cancellation of some activities. This represent a serious level of pain (depending on how “critical” the cancelled activities were.


The “pain from warming” is itself an aggregated representation of the various impacts, as show with the “red dotted zone” in the following figure. Pain here is a subjective factor (used as a trigger), what matters is to find a way to assess in a homogeneous way the pain from the different factors. The following figure makes explicit the difference from seeing (empathy) a catastrophe, from fearing (the occurrence of) a catastrophe and from enduring a catastrophe.

CCEM as a tool to test and hone your own beliefs

The following figure describes the intent of making beliefs explicit in CCEM. The CCEM simulation model is made of state variables that describe earth as a complex system, and simulation rules that we decompose into:

·       The foundations, such as the IPCC “warming as a consequence of CO2”, the economic growth model, or the supply/demand adjustment loop. As pointed out in the figure, these foundations represent the backbone of the simulation model. They are the assumption that are not challenged (which is why it is important that they are shared with the previously quoted earth models).

·       Beliefs as parameters to the model, that will be described in the remainder of the paper. These are only “hypotheses” that can be modified easily. The most interesting way of using the CCEM model is to use the simulation results to challenge your own beliefs (Caseau, 2012).