IPCC Special Report on Emissions Scenarios

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IV.5. The Multiregional Approach for Resource and Industry Allocation Model (MARIA)

The Multiregional Approach for Resource and Industry Allocation Model (MARIA) is a compact integrated assessment model to assess the interrelationships among the economy, energy, resources, land use, and global climate change (Mori and Takahashi, 1999; Mori 2000). The origin of the model is the Dynamic Integrated Model of Climate and the Economy (DICE) model, developed by Nordhaus (1994). Involving energy flows and dividing the world into regions, MARIA has been developed to assess technology and policy options to address global warming. Like Global 2100 developed by Manne and Richels (1992), MARIA is currently an intertemporal non-linear optimization model that deals with international trading among eight regions - NAM (USA and Canada), Japan, Other OECD countries, China, ASEAN countries (Indonesia, Malaysia, Philippines, Singapore, Republic of Korea, Thailand), SAS (India, Bangladesh, Pakistan, Sri-Lanka), EEFSU (Eastern Europe and the Former Soviet Union), and ALM (Africa and Latin America). It also encompasses energy flows and simplified food production and land use changes to show the potential contribution of biomass.

Economic activities are represented by a constant elasticity of substitution (CES) production function with capital stock, labor, electricity, and non-electric energy set for the above eight world regions. Future GDP growth is projected by considering potential GDP growth rates (the product of two exogenous assumptions - population and potential per capita GDP growth) as well as endogenously determined energy costs and prices. The energy module in MARIA involves three fossil primary energy resources (i.e., coal, natural gas, and oil), biomass, nuclear power, and renewable energy technologies (e.g., hydropower, solar, wind, and geothermal). Energy demand consists of industry, transportation, and other public uses. Nuclear fuel recycling technologies are simply but explicitly formulated. Carbon sequestration technologies are also taken into account. Typically, MARIA basically generates resource extraction profiles in which gas is mainly used in the first half of the 21^st century, and subsequently carbon-free sources (e.g., solar, nuclear, and biomass) and coal assume the main roles in the second half of the 21^st century.

Energy costs in the model consist of energy production and utilization costs. Market prices are determined endogenously on the basis of model-calculated shadow prices. Among various parameters, the extraction costs of fossil fuel resources and energy conversion cost coefficients contribute substantially to determining the model's energy mix and emissions. The latest model version, MARIA-8, applied Rogner's estimates on fossil resource availability (Rogner, 1997). For the sake of simplicity, the fossil resource and reserve categories are aggregated into two classes, assuming a quadratic production function to interpolate the relationships between resource occurrences and extraction costs. Corresponding model parameters are summarized in Table IV-6. The cost coefficients of energy conversion technologies are basically extracted from the GLOBAL 2100 model (Manne and Richels, 1992). The basic values used in the case of the B2 scenario are illustrated in Table IV-7, and important model parameters deployed for MARIA's other SRES scenario quantifications are shown in Table IV-8. Other energy-related cost parameters correspond to renewable energy sources, methanol and ethanol processes, nuclear fuel recycle, carbon sequestration, etc. They are described in more detail in Mori and Takahashi (1999).

International trade prices are generated by the Lagrange multipliers of the corresponding constraints as a feature of optimization models. The Negishi weight technique was employed to assess the international equilibrium prices of tradable goods under the budget constraints (Negishi, 1972). Illustrative international energy trade prices for scenario B2 are summarized in Chapter 4 and are not repeated here.

The Global Warming Subsystem in MARIA is based on Wigley's five-time constant model for the emission-concentration mechanism. A two-level thermal reservoir model is also employed following the DICE model (Wigley, 1994; Nordhaus, 1994). Only global carbon emissions are currently treated in this model component.

MARIA's Food and Land Use module serves to assess the potential contributions of biomass. A simplified food demand and land-use subsystem was included. Nutrition, calorie, and protein demand is a function of per capita income. Either directly or via meat, crop and pasture supply these demands. Forests are a source of biomass and wood products, but also their function as a carbon sink is evaluated. The relationships among the above-mentioned subsystems are shown in Figure IV-5.

Since MARIA is designed for macro-level evaluation of various options consistently, detailed information, such as gridded SO2 emissions, industrial structure change, and urbanization issues, is not generated. However, MARIA can provide long-term profiles of fuel mix changes and possible trade premiums under various scenarios.

More detailed information can be obtained by referring to the following web site: http://shun-sea.ia.noda.sut.ac.jp/indexj.html.