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Research Programs

Integrated Assessment Modeling

Integrated assessment for climate change assembles knowledge from a diverse set of sources, relevant to one or more aspects of the climate change issue, for the purpose of gaining insights that would not otherwise be available from traditional, disciplinary, research.
- Jae Edmonds, GTSP Chief Scientist, From "Comments on Integrated Assessment Modeling of Climate Change"

Integrated assessment can be described as an analysis methodology that combines information pertaining to economic, energy and climate variables across various scientific disciplines, time, and spatial scales. As a platform for integrating knowledge, the design of an Integrated Assessment model requires a set of tradeoffs between speed, complexity, sectoral coverage, flexibility, and ease of use. Models range from those oriented toward academic research to those developed explicitly for a policy context. Simple models are often used to explore system behavior while more complex models are aimed at representing a large number of relevant processes and interactions.

Pacific Northwest National Laboratory (PNNL) has been at the forefront of global energy/economic modeling for nearly two decades. PNNL's models were the primary analytical tools for the U.S.'s analysis of the 1992 UN Framework Convention as well as the 1997 Kyoto Protocol. Our modeling and analysis of carbon dioxide concentration stabilization pathways, pointing to the importance of technology in addressing climate change challenges, has set the agenda for the U.S.'s response to the climate change problem. Several leading international energy companies have also used our models and analysis for their own strategic planning.

The PNNL models, designed for policy-relevant research, include a comprehensive representation of energy production and consumption in an economically consistent global framework with regional detail. A global scope and century time scale is necessary given the long-term nature of the climate problem. Responses to climate change, however, will occur at a regional and corporate level, with key issues being the economics and practicalities of technology penetration and policy implementation in both the near and long term. Our models

Given our focus on energy systems, our models contain realistic, physically based, representations of energy production systems. Electricity production, for example, is modeled at the technology level (e.g., oil-fired, coal-fired, nuclear, solar PV, etc.). We also include an agriculture and land-use model that calculates the potential supply of commercial biomass fuels and the tradeoff between production of biomass and other land uses. This is in contrast to models that contain more abstract economic descriptions of energy production.

The impact of policies and technology deployment decisions need to be examined in the context of an integrated global economy. Actions in one sector or region cannot be examined in isolation. Our research is designed to answer specific questions about economic impacts, new markets, and the value of new technologies to help inform a well balanced dialogue on how best to address climate change. Our attention to technological detail and our extensive experience in analyzing energy policies and markets distinguishes our work from other programs.

The PNNL models and related analysis tools help answer a wide variety of questions that are relevant to strategic technology and policy decisions. Examples of the kinds of questions we have addressed are shown below:

In addition to these specific questions, there is a set of issues around understanding potential technology pathways, the dynamic interaction of those technology options, and managing the cost of transition from our current state to one of several potential future energy systems that put us on a path to lower emissions and stabilization in the longer term.

Current Modeling Platforms

The Components (atmospheric composition, climate & sea level, human activities, and ecosystems) and interactions within Integrated Assessment Models
Figure 1: The Components of Integrated Assessment Models

At present we use two mature modeling platforms for our analysis work, the Mini-Climate Assessment Model (MiniCAM) and the Second Generation Model (SGM). They are a part of an overall integrated modeling system, referred to as the Global Change Assessment Model (GCAM), which is used to understand the role energy technology plays in shaping the long-term emission of greenhouse gases into the atmosphere. An important aspect of GCAM is its ability to model the dynamics of the interactions among the four principal sets of processes that characterize the global change problem: 1) human activities, 2) atmospheric composition, 3) climate and sea level, and 4) terrestrial ecosystems. Different models handle these sets of processes, with interfaces defined among them. The principal model used for human activities is the SGM, which is an integral part of GCAM. A representation of those interactions is shown in Figure 1.

The MiniCAM is a long-term, partial-equilibrium model of the energy, agriculture, and climate system, a reduced form of the GCAM. It contains an emissions model that considers both energy and land use emissions. It considers the full range of greenhouse gases and the major new alternative technologies that are pertinent to questions about the future structure of energy supply. The MiniCAM is used for modeling over long time scales where the characteristics of existing capital stocks are not the dominant factor in determining the dynamics of the energy system.

A wide range of technologies, fuels, and energy carriers can be used to supply end-use energy demands. The MiniCAM can produce an end-to-end analysis of energy supply and demand, emissions of greenhouse gases and local air pollutants, and mitigation costs. The MiniCAM is fast and flexible and can be used to examine a large number of alternative future scenarios. Its principal usefulness has been in evaluating technology portfolios to address climate change, at both the global and regional levels, and in evaluating global emissions under a variety of technology and policy scenarios.

The SGM is a set of 14 regional computable- general- equilibrium (CGE) models, with an emphasis on energy transformation, energy consumption, and greenhouse gas emissions. Regional models may be run independently or as a system with international trade in carbon emissions rights. The SGM is used for analysis over several decades (up to 2050) and is designed specifically to address issues associated with global change, including 1) projecting baseline carbon emissions over time for a country or group of countries; 2) determining the least-cost way to meet any particular emissions constraint; and 3) providing an estimate of the overall cost of meeting an emissions target. The CGE framework of the SGM provides a state-of-the art methodology for estimating near-term climate mitigation costs.