Fairness, climate change and population – FAIR-CLIMPOP

This project combines standard tools of economic analysis (mathematical modeling of phenomena and analyses of different economic contexts ; axiomatic analysis) and computer simulation tools to model the climate-economy interaction. The latter tools make it possible to project future joint evolution of the economy, demography and climate.

We have proposed several alternative models to describe different ethical / political positions on the value of population sizes and the value of longevity for human well-being.

We have developed an endogenous population module in an integrated economy-climate assessment model. This module reproduces the trajectories of existing models in the absence of climate impacts and is consistent with existing studies when this endogenous effect is taken into account.

Our theoretical and methodological work describing different ethical / political positions on the value of population sizes and longevity for human well-being will need to be applied to more realistic models.

Our endogenous population module could be combined with other economic-climate assessment models to provide a more comprehensive analysis of equity issues (for example by integrating the issue of income inequality).

Marc FLEURBAEY, Stéphane ZUBER. «Fair utilitarianism«, CES Working Paper, No 2017.05R

Geir ASHEIM, Stéphane ZUBER. «Rank-discounting as a solution to a dilemma in population ethics«, CES Working Paper, No 2017.41

Aurélie MEJEAN, Marc FLEURBAEY, Antonin POTTIER, Stéphane ZUBER. «Intergenerational equity under catastrophic climate change«, CES Working Paper, No 2017.40

Marc FLEURBAEY, Marie-Louise LEROUX, Pierre PESTIEAU, Grégory PONTHIERE, Stéphane ZUBER. «Premature deaths, accidental bequests and fairness«, PSE Working Paper, No 2017-52

Recent research about climate change has revived old concerns about a possible conflict between human development and population size. Economic growth accelerates climate change, inducing large impacts on agriculture (threatening livelihood especially in developing countries) and more directly affecting mortality risk through extreme events and increase in the prevalence of some diseases. In this project, we seek to include demographic impacts on population size when evaluating climate policies. We want first to define normative principles that can govern the evaluation of demographic impacts of climate change and design new evaluation tools (social welfare criteria). We then want to study their implications for climate policy in an Integrated Assessment Model (IAM) of the economy and the climate, which we will develop from existing models by making population size endogenous. The new evaluation tools must allow the comparisons of populations of different sizes and better take into account longevity in the definition of wellbeing indices.
This project thus has three ambitious and original objectives. The first objective is to deepen our knowledge of normative criteria to evaluate policies affecting population size. With respect to the existing literature, the project will consider new approaches outside a broad utilitarian family and will focus on fairness principles, in a multidimensional perspective accounting for the distribution of market and non-market goods. The second objective is to better take into account longevity in the definition of wellbeing indices. To discuss fairness between generations, it is crucial to be able to compare individuals with different lifespans, given that improvements or worsening on life expectancy are key elements of human development. We will ground the value of life expectancy in people preferences. The third objective is to better understand the implications of normative choices for the design of policies in an IAM. A preliminary task will consist in building a new IAM that endogenizes mortality from climate change. This requires including a more disaggregated age structure in the model with age-specific mortality and fertility rates to produce an endogenous population dynamics that also includes effects on the size of new generations. With this new IAM, we will then be able to consider different policies and order them using the alternative normative criteria developed in other parts of the project. In particular, this may allow us to discuss to what extent more egalitarian principles and criteria giving more value to lifespans and population size promote stronger climate policies.
From the scientific point of view, the project will provide new insights and contribute to enhancing knowledge both from a normative and a positive perspective. The project will also have a broader societal impact by bringing a better understanding of the long-term impacts of climate change and the possibility of long-term sustainable development accounting for demographic aspects. The project aims at developing an integrative approach combing economic, demographic and climatic risks. Its results will thus be of interest to the general public and to decision-makers in terms of policy design.