The world is currently facing multiple crises that interact with each other, such as climate change, financial instability, increasing inequalities, and resource depletion – to name only a few. To cope with these challenges, the GEJP develops various modeling tools that help build scenarios of the future and provide support for policy decisions. 

Developing such tools requires creating strong interdisciplinary connections between economics and natural sciences. On the economics side, our models emphasize the macroeconomic dynamics of investment, employment, inequality distributions, and private debt. On the environmental side, they analyze the effects of human activities on the climate and the availability of energy and materials. Thus, our models can provide an overall picture of the main issues that will confront human societies in the coming decades and help design a way forward.

Comprehensive Modeling

The Challenge

We are currently entering the Anthropocene: through our creations and our capital, humanity is now able to biophysically disrupt the functions of our common home, our ecosystem. 

Not everyone is equally responsible for this multifaceted crisis. Unfortunately, the ones who are least responsible are the ones who suffer the most. As written in Laudato Si’ by Pope Francis, the exploitation of the environment shares its roots with the causes of the exploitation of humans by humans. 

To solve the ecological crisis, we must address the root causes of inequality, and act to halt the irreversible degradation of our environment. There will be either a sustainable transition toward an environmentally just world or a shift to an uninhabitable world.

Specific questions for environmental justice 

Confronting the challenge leads to particular ethical and practical questions related to environmental justice, for example:

The need for models

These questions are systemic and require a holistic approach that can combine an understanding of our biophysical world on one side and our socio-economic structure on the other. It requires a bold approach that can describe crises and allow for phased transitions. It also needs to encourage the different stakeholders to appropriate its characteristics and contribute to an interdisciplinary dialogue.

Thinking long-term is tough, and expert, holistic thinking is beyond any one person’s ability.  We need to create a logical structure that can host and address the properties and the processes of our world that can be used as a compass to lead us in the right direction. That is the main goal of modeling: the scientific method of putting data together with interactions between them, and studying their behavior over time. While models are ubiquitous, building the right model for the right questions requires mathematical, interdisciplinary, and epistemological expertise. 

The models

To cope with these challenges, the Georgetown Environmental Justice Program (GEJP) develops various models to explore possible future actions and assist in decision-making. 

Different models, like bricks, represent the different components of the Earth system and human societies and can be assembled – coupled – in different ways as needed. That way, each project can be as simple as possible, while as complete as necessary.

At the core is our socioeconomic system, represented by our economic production and its interaction with the citizens. This macroeconomic system emphasizes the dynamics of investment, unemployment, debt, and inequalities. It is constructed on a stock-flux consistent structure: nothing can appear or disappear without explicit phenomena behind it, respecting the principles of thermodynamics. This system is then coupled with biophysical modules such as climate models, up to a high spatial resolution that provides climate impact projections with a 50km2-granularity using ILOVECLIM, an intermediate complexity climate model.

Construction of our models: at the center is our fundamental structure that connects production and household. The description of their relation can be refined, and aggregates explored. We can also connect financial markets models, as well as resource uptake or biodiversity impacts. 

In the wake of the limits to growth report from 1972, those models are based on the mathematical properties of dynamical systems, creating out-of-equilibrium dynamics that can either find the right organization or lead to crises. It takes elements from complexity science and self-organization, as well as the notion of dissipative systems from biophysics, and trophic networks from ecology. The economic side is based on stock-flow-consistency and agent-based models, with heuristic human behavior, and input-output production dynamics. Energy is taken into account naturally, at the center of the production process. 

In consequence, those models are simple in their construction through modules, but complex through the richness of their interactions. They can be studied as components or as a whole and can describe equilibrium as a neoclassical economic model, but also alternative path and their potential instabilities. They reconstruct most traditional indicators but also provide some transitional insight, using the movement of a transitory economy to its advantage. 

An illustrative figure of a climate-economy coupling. There are four modules : (left) an economic structure with private debt, employment and wage share, and production, (top) a decarbonation module with a carbon pricing and a green technology price, (right) a climate model, and (bottom, white) damages from the temperature increase on the economy. Each field (name) corresponds to a variable and an equation that is solved analytically or numerically.