dc.description.abstract | The goal of this thesis is to build a reduced-complexity model of coupled
climate─economy─biosphere interactions, which uses the minimum number of variables and
equations needed to capture the fundamental mechanisms involved and can thus help clarify the
role of the different variables and parameters. The Coupled Climate─Economy─Biosphere
(CoCEB) model described herein takes an integrated assessment approach to simulating global
change. By using an endogenous growth module with physical and human capital accumulation,
this thesis considers the sustainability of economic growth, as economic activity intensifies
greenhouse gas emissions that in turn cause economic damage due to climate change. Various
climate change mitigation policy measures are considered. While many integrated assessment
models treat abatement costs merely as an unproductive loss of income, this thesis considers
abatement activities also as an investment in increase of overall energy efficiency of the economy
and decrease of overall carbon intensity of the energy system.
One of the major drawbacks of integrated assessment models is that they mainly focus on
mitigation in the energy sector and consider emissions from land-use as exogenous. Since
greenhouse gas emissions from deforestation and current terrestrial uptake are significant, it is
important to include mitigation of these emissions in the biota sinks within integrated assessment
models. Several studies suggest that forest carbon sequestration can help reduce atmospheric
carbon concentration significantly and is a cost efficient way to curb the prevailing climate change.
This thesis also looks at relevant economic aspects of deforestation control and carbon
sequestration in forests as well as the efficiency of carbon capture and storage (CCS) technologies
as policy measures for climate change mitigation.
Because full realistic coupled climate models are so complex, analyses of the various
potential feedbacks between climate, economy, and biosphere have been rather limited. Potentially
important mechanisms are better initially described in low or intermediate complexity models.
The CoCEB is a formal framework in which it is possible to represent in a simple way
different elements of the coupled system and their interactions. The model developed, being an
exercise in simplicity and not a predictive tool for climate change impacts, brings together and
summarizes information from diverse literature on climate change mitigation measures and their
associated costs, and allows comparing them in a coherent way.
The model is, of course sensitive, to the choice of key parameters and in particular the
parameters setting the costs of the different means of climate change mitigation: the parameter
values tested span the range of cost values found in literature.
The thesis shows that: i) investment in low-carbon technologies helps to reduce the volume
of industrial carbon emissions, lower temperature deviations, and lead to positive effects in the
long term economic growth; ii) low investment in CCS contributes to reducing industrial carbon
emissions and to increasing gross domestic product (GDP), but further investment leads to a
smaller reduction in emissions, as well as in the incremental GDP growth; iii) enhanced
deforestation control contributes to a reduction in both deforestation emissions and atmospheric
carbon dioxide concentration, thus reducing the impacts of climate change and contributing to a
slight appreciation of GDP growth, an effect that is very small, though, compared to that of lowcarbon technologies or CCS; and iv) the results in i) and ii) remain very sensitive to the
formulation of technological improvements costs. To the contrary, the results for deforestation
control are less sensitive to the formulation of its cost. A large range of hypotheses on these costs
appear in the literature, and our modeling framework permitted to span this range and check the
sensitivity of results The sensitivity study is not intended to make precise calibrations; rather, it is
meant to provide a tool for studying qualitatively how various climate policies affect the economy. | en_US |