Model

CAVEAT:   This web site is under construction. The model description is not complete nor fool-proofed yet.


CCEM is defined as the coupling of five coarse models. The “coarse” adjective of CCEM captures the following design intent:


·       Keep the model simple for readability, so that you can decide quickly whether you agree with this approach or not. However, sophisticated the earth model might be, it remains a very crude abstraction, so readability is more important than completeness..

·       Support fast simulation runs, since the goal is to perform millions of runs when exploring as a complex game with multiple players, using GTES simulation framework.

·     Make the beliefs visible, easy to understand and to modify, so that CCEM may be used to explore one’s own mental models, as explained in the motivation section.


The following figure illustrates the complete CCEM system, following John Sterman notations (Sterman, 2000), that is how each of the five model interacts with each other.

CCEM is a simulation model, where earth is considered a complex system, its various energy/ economy/ climate components being described by state variables (a few hundreds), that vary in time. Time is discretized and the model describes how each component of the model evolve year after year. The overall structure of a simulation run may be described by the following figure. The starting point is 2010, first because the work presented here started a decade ago but also because it makes 2020 an interesting point for calibration. Each component is defined by a “discretized differential equation” that gives the value of the state variables associated to energy production, energy consumption, energy transition, economic output, temperature elevation and its consequence at year y as functions of the state variables’ value the year before.

M1: Energy Production


The M1 model answers the two questions: (a) “How much fossil energy can we access, at which costs?” (b) “How much clean energy could be made available in the future, at which costs?”. CCEM distinguishes between three fossil fuels: oil, gas and coal, while regrouping all “clean” sources (wind, solar, hydro, nuclear) into one. For M1, we only consider primary sources of energies (M3 will take secondary forms and usage of energy into account).

M1 description may be found here


M2: Energy Consumption

The model M2 captures the answer to the question “How is each part of our GDP dependent on energy?”. Some economic activities are very sensitive to energy since energy is one of their major costs associated with value creation.

M2 description may be found here.

M3: Energy Transition


The Energy Transition model captures the question “How fast can we substitute from one source of primary energy to another?” (Püttgen, 2022). For each transition, our “belief” is a roadmap, a function that tells for each year which share of energy consumption may be transferred to another source. Since there are four kinds of primary energy in the CCEM model, and since we assume transitions to be oriented (a simplifying assumption), there are six transitions to consider: Coal to Oil (using CTL techniques), Coal to Gas (which we have seen a fair amount in the US during the last decade), Coal to Clean, Oil to Gas, Oil to Clean, and Gas to Clean.

M3's description may be found here

M4:  World Economy

The world economy model (M4) represents the question “which GDP is produced from a given amount of investment, technology, energy and workforce ?”. It uses a simple exponential growth model (as is the case of most earth models) based on productive assets creating value over a unit of time through the use of energy.

M4 description may be found here.


M5: Ecological Redirection

The M5 Model answers the question “What kind of consequences should we expect from the global warming forecasted by the IPCC models?”. There are three successive sub-questions:

·       What is the temperature elevation produced by the raise of CO2 (and other greenhouse gas)?

·       What are the economic consequences of this warming? (mostly, the SCC question)

·       How will the humanity react (from the population to the economy as a system)?

find more about M5 here

CCEM Known Limitations

CCEM is a federation of "coarse" (i.e. simple) models. Although it is modular since key sub-components (beliefs, a.k.a., "known unknowns") are parameter that may be changed at will, it still relies of a set of simplifying assumption that are obvisouly debatable.

Without a pretense of completeness, here are the most obvious limitations