Download Toth, 2003. Integrated assessment of climate protection strategies

INTEGRATED ASSESSMENT OF CLIMATE
PROTECTION STRATEGIES
Guest Editorial
Stabilizing the earth’s atmosphere in terms of anthropogenic interference remains
the key issue in managing the risk of climate change ten years after signing the
United Nations Framework Convention on Climate Change (UNFCCC). What is
the nature and magnitude of climate change impacts that constitute ‘dangerous’
interference with the climate system? What is the associated level of greenhousegas concentrations in the atmosphere? What is the desirable timing of emissions
control actions considering the multitude of implications that range from the rate
of warming and its impacts to the technology dynamics and the resulting mitigation costs. What is the ensuing balance of the required adaptation and mitigation
actions and costs in different world regions? In which regions is it most practical
to start emissions reductions and which principles and practicalities should guide
the burden sharing?
Integrated assessment models combining fundamental elements of the global
climate and socioeconomic systems have become the principal instruments to explore these questions and to provide insights for climate policy. These were the
central objectives of the project on Integrated Assessment of Climate Protection
Strategies (ICLIPS) as well. The project was implemented by an international consortium of six research centers together with a core team at the Potsdam Institute
for Climate Impact Research (PIK). The main focus of the ICLIPS project was on
the long-term dynamics of the interactions between human society and the climate
system. The conceptual foundation of the project is the so-called tolerable windows
approach, also called the inverse or guardrail approach. It seeks to identify fields
of long-term GHG emission paths that will prevent climate change resulting in
unacceptable regional or sectoral impacts without instigating intolerable mitigation
costs. The limits to unacceptable impacts and costs are normative judgments based
on the values and perceptions of social actors and serve as user-specified input to
the ICLIPS integrated assessment model.
The above questions concerning long-term climate change policies will be high
on the policy agenda over the next few years as delegates to the UNFCCC process
will be preparing for negotiating emissions reduction agreements for the second
commitment period with 2020 as the expected target year. A meaningful contemplation of near-term emissions reduction goals requires the thorough consideration
of the possible range of long-term stabilization levels. Which choices remain open
and which options get foreclosed in terms of climate change and impacts under
Climatic Change 56: 1–5, 2003.
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alternative near-term emissions targets, given our present knowledge about the fate
of greenhouse gases in the atmosphere, about their impacts on the global biogeochemical cycles and the climate system, and about the inertia characterizing both
the socioeconomic and the climate systems. Considering the immense uncertainties
of our knowledge about these processes, policy-relevant insights about long-term
options need to be framed in the context of sequential decision making allowing
for future learning and ensuing course correction.
This special issue is devoted to exploring the scientific, methodological, and
policy aspects of long-term climate change. Papers present the ICLIPS integrated
assessment framework, the various types of analyses it can perform, and the kinds
of results it can produce. The central theme revolves around the crucial trade-offs
in long-term climate policy: what do we aspire to avoid in terms of climate change
impacts and what can we get in terms of greenhouse gas mitigation expenditures.
The introductory paper by Toth provides an overview of the project, its conceptual foundations and relationships to other decision analytical frameworks adopted
in recent integrated assessment models, as well as a detailed roadmap to the material presented in the special issue. This is followed by three papers presenting the
ICLIPS framework and the main components of the integrated assessment model
(Toth et al. – Part 1), the long-term emissions corridors as the most distinctive
results and insights the model can provide (Toth et al. – Part 2), and the methodological foundations and computational procedures for producing those results
(Bruckner et al. – Method).
The next set of papers provides detailed documentations of the principal components in the ICLIPS framework: the procedures and models to establish climate
impact response functions for different impact sectors and the ways of using them
in various ways (Füssel et al.), the ICLIPS greenhouse gas, carbon cycle, and climate model and its possible uses (Bruckner et al. – Climate), and the aggregated
economic model and its possible applications to establish baseline emissions paths,
as well as emissions corridors and cost-minimizing paths under various combinations of impact and mitigation cost constraints (Leimbach and Toth). The final
group of papers presents additional components: the method and data sources for
deriving dynamic mitigation cost functions incorporated in the aggregated economic model (Gritsevskyi and Schrattenholzer), the model to compute and account
for GHG emissions from land-use change and agriculture in the ICLIPS framework
(Sands and Leimbach), and, as a somewhat more distant but very important family
member, the global multi-region, multi-sector general equilibrium model covering
a much shorter time horizon than the integrated model, but providing much more
detail about the regional and sectoral costs of medium-term mitigation strategies
(Klepper and Springer).
Just as all other integrated assessment activities, the ICLIPS project involved
many disciplines from natural and social sciences. This feature is reflected in the
subsequent papers and hopefully it makes this special issue an interesting reading
for the broad interdisciplinary readership of Climatic Change. The level of techni-
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cal detail of the presentation varies across the papers but a great deal of effort has
been devoted to trimming down disciplinary jargon and to increasing transparency.
The modular nature of the ICLIPS framework allows taking out selected modules,
establishing the appropriate data exchange platforms, and using the modules in
other integrated models. Accordingly, detailed presentations of the components
in the ICLIPS framework are intended to serve the transparency of the results
presented in this special issue as well the transferability of the components to other
integrated assessment models.
To fulfill the criteria of model transparency, most papers in the special issue
are methodologically rather complex and rich in technical detail. As a small compensation to readers who pore over those modeling discourses, each paper includes
sections with model outcomes and their interpretation: comprehensive results stemming from the integrated assessment framework and module-specific results that
demonstrate the operational features and particular capabilities of the individual
modules.
To begin with the latter, papers dealing with the various components of the
integrated framework highlight model outcomes that have some novel features or
make comparison with results of other integrated assessment models easier. The
ICLIPS climate model can be used to assess how ‘reachable climate domains’
(for example, combinations of atmospheric CO2 concentrations and the globally
averaged near-surface temperature) can evolve over time under certain restrictions for plausible emissions paths. By following the procedures presented in the
impact response functions paper, climate impact assessors and stakeholders can
use (regional) climate scenarios and impact models to produce their own climate
impact response functions for the sectors and regions of their interest to explore
the relationships between the relevant climatic variables and the sectoral/regional
impact indicator across a wide range of plausible futures. Finally, one set of results
presented in the paper dealing with the economic model demonstrates that, when
using similar economic efficiency principles (cost minimization), seemingly quite
different models – ICLIPS and the models underlying the Wigley et al. (1996)
analysis – lead to fairly similar insights about the long-term emission paths despite
the different decision-analytical frameworks, model formulation, regionalization,
and parameterization.
Typical examples of the comprehensive results are the series of carbon emission
corridors under different normative constraints and modeling assumptions presented in the papers documenting the integrated assessment model. The emission
corridors delineate the future space for climate policy in the sense that any emission
path surpassing its boundary clearly violates at least one of the user-specified constraints for managing the risk of climate change. The limits to socially acceptable
climate change impacts – whichever sectors or regions are their sources – play a
particularly important role in determining the existence and shape of the emission
policy space, especially in the low impact tolerance domain. Yet the corridor is also
shaped by the limits set to emission reduction costs and to the allowed mechanisms
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to reduce them (permit trading) as well as by the timing of the mitigation action.
These multifaceted relationships are explored from different perspectives in the
papers that follow.
These complex relationships make international negotiations concerning longterm climate mitigation targets highly contentious and the agreement on a generally
acceptable medium-term emissions reduction target extremely difficult (witness the
Kyoto process). However, integrated assessment modeling of the climate change
problem has reached the level of maturity by now at which using the integrated
model presented here – together with a number of other models producing comparable results – in national and international preparatory meetings prior to the
formal negotiations might help establish the shared understanding among the negotiators. This could foster reaching an agreement in the official negotiations forum.
The participatory techniques (e.g., Policy Exercises) providing the organizationalprocedural framework for such activities are well-established (Toth, 1988) and
used in various fields, and have been tested in the climate change area (Parson,
1997). What is needed is a widely respected host and the political will of the key
stakeholders to engage into such an exploratory activity.
In a landmark paper on integrated assessment modeling of global climate
change, Schneider (1997) provided a checklist of issues and practices modelers should keep in mind. Somewhat paraphrased, the list includes the following:
specify the limited context of your exercise, contrast your model to alternative
approaches, provide ample choices for users to specify culturally-dependent factors
and surprises, perform many ‘validation’ tests, stress that results will be changing
as new information leads to ‘rolling reassessments’, note components that are particularly sensitive to current controversies. By taking a final look at this special
issue as it goes to press, I believe that contributors to the ICLIPS project and to the
papers that follow did a reasonably good – albeit far from perfect – job on most
of these criteria. For that reason, my hope is that this special issue makes at least
a small contribution to moving integrated assessment models from the realm of
the ‘opaque screen hiding value-laden assumptions’ towards the promised land of
‘transparent rational tool for policy making’.
Finally, I would like to thank all authors for their contributions to the project
and to this special issue. I am most grateful to the large number of referees who
provided exceptionally thoughtful guidance for improving the papers. I also thank
Eva Hizsnyik, who was the technical coordinator of the ICLIPS project and supervised the production of this special issue. We are all indebted to Steve Schneider
for his inspiration over the years as we were working on the project and for his
encouragement to present our results. Special thanks are due to Katarina Kivel for
her patience and help throughout the production process.
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References
Parson, E. A.: 1998, ‘Informing Global Environmental Policy Making: A Plea for New Methods of
Assessment and Synthesis’, Environmental Modeling and Assessment 2, 267–279.
Schneider, S. H.: 1997, ‘Integrated Assessment Modeling of Global Climate Change: Transparent Rational Tool for Policy Making or Opaque Screen Hiding Value-Laden Assumptions?’,
Environmental Modeling and Assessment 2, 229–249.
Toth, F. L.: 1988, ‘Policy Exercises’, Simulation & Games 19, 235–276.
Wigley, T. M. L., Richels, R., and Edmonds, J. A.: 1996, ‘Economic and Environmental Choices in
the Stabilization of Atmospheric CO2 Concentrations’, Nature 379, 240–243.
ICLIPS Project Leader 1996–2001,
PIK – Potsdam Institute for Climate Impact Research,
Potsdam, Germany
Present affiliation:
IIASA – International Institute for Applied Systems Analysis,
Schlossplatz 1, A-2361 Laxenburg, Austria,
E-mail: [email protected]
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