Download TITLE: The Integrating Assessment Modeling Community: overview

TITLE: The Integrating Assessment Modeling Community: overview, structuring and interactions
with the IPCC expertise
The intellectual debates expressed by the Club of Rome about the “Limits to Growth” (Meadows,
1972) and the oil crisis in the 70s have given rise to energy-environment-economy (E3) models to
explore the feasibility of long-term development pathways. The rise of climate change on the public
agenda since the late 80s has prompted the need for quantitative assessment of mitigation
strategies, in particular in view of the IPCC reports. E3 models gather different types of models, in
particular IAMs (Integrated Assessment models). IAMs are simplified, stylized, numerical approaches
to represent complex physical and social systems, and the most relevant interactions among the
systems (e.g., energy, agriculture, the economic system). From a set of input assumptions they
produce outputs in the form of quantified scenarios: energy system transitions, land use transitions,
economic effects of mitigation, emissions trajectories. These scenarios are central to the work of the
IPCC “Working Group III” on mitigation of climate change, and play an increasingly important part in
the negotiation and elaboration of climate policies.
In this paper, we investigate the conditions of the production of such scenarios and the diversity of
the models behind them. These models have been developped by an heterogeneous,
interdisciplinary community of research. This paper analyses the development and the evolution of
this community since the early 90s and provides an overview of the main models and research
teams. The climate debate fostered the rise of a new generation of models in the vein of the first
global and technico-economic models developed in the 60s and 80s. A main divide in the 90s was
between macro-economic models (top-down) and more engineer styles models (bottom up).
Bottom-up models give the priority to a detailed description of technologies and sectoral systems,
while top-down models represent macro-economic consistency but encapsulate a limited description
of technologies. The gap has narrowed and an increasing number of hybrid models now combine
comprehensive top-down representations of macro-economic processes with a technologically
explicit bottom-up representation of energy systems.
We explain this narrowing gap as a result of the structuring of the IAM community. How did these
models emerge as unified – though diverse – category? How and where did the IAM community
organise as such, and what is it made of? This paper stresses the role of intercomparison modeling
exercises under the framework of key institutions (for instance the Energy Modeling Forum
coordinated by Stanford University, European Framework projects…). It traces the development of
an epistemic community which participates, through the production of socio-eoconomic scenarios,
to the framing of the assessment of climate policies in group III of the IPCC. This history of the
development of IAM relies on a mapping of existing models and modeling team, on interviews, as
well as on an analysis of the content of the research programs conducted in these forums, the
material produced (reports, articles, IPCC assessment reports in particular AR4 and 5…).