Emissions Scenarios

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IV.2. The Atmospheric Stabilization Framework (ASF) Model

The current version of ASF includes energy, agricultural, and deforestation GHG emissions and atmospheric models and provides emission estimates for nine world regions (Tables IV-1 and IV-2).

Figure IV-2: Overview of the IMAGE EIS/TIMER model.

In the ASF model balancing the supply and demand for energy is achieved ultimately by adjusting energy prices. Energy prices differ by region to reflect regional market conditions, and by type of energy to reflect supply constraints, conversion costs, and the value of the energy to end users. ASF estimates the supply-demand balance by an iterative search technique to determine supply prices. These supply prices, which energy producers charge for the fuel at the wellhead or at the mine, are used to estimate the secondary energy prices in each region. These secondary prices are based on the supply price for the marginal export region, the interregional transportation cost, refining and distribution costs, and regional tax policies. For electricity, the secondary prices reflect the relative proportions of each fuel used to produce the electricity, the secondary prices of those fuels, the non-fossil costs of converting the fuels into electricity, and the conversion efficiency.

The agricultural ASF model estimates the production of major agricultural products, such as meat, milk, and grain, which is driven by population and gross national product (GNP) growth. This model is linked with the ASF deforestation model, which estimates the area of land deforested annually as a function of population growth and demand for agricultural products.

The ASF GHG emissions model uses outputs of the energy, agricultural, and deforestation models to estimate GHG emissions in each ASF region. These emissions are estimated by mapping GHG emission sources to the corresponding emission drivers and changing them according to changes in these drivers. For example, CH4 emissions from landfills are mapped to population, while CO2 emissions from cement production are mapped to GNP.

Finally, the ASF atmospheric model uses GHG emission estimates to calculate GHG concentrations, and corresponding radiative forcing and temperature effects. A detailed description of the ASF is provided in the ASF 1990 Report to Congress (Lashof and Tirpak, 1990), and recent applications of the model are reported in Pepper et al. (1998) and Sankovski et al. (2000).

IV.3. Integrated Model to Assess the Greenhouse Effect

The Integrated Model to Assess the Greenhouse Effect (IMAGE 2) consists of three fully linked systems of models:

  • The Energy-Industry System (EIS).
  • The Terrestrial Environment System (TES).
  • The Atmosphere-Ocean System (AOS).

Figure IV-3: The structure of the TES of IMAGE 2 (including links to other modules).

Table IV-3: IMAGE 2 regions (see also Table IV-I).

Latin America (Central and South)
OECD Europe
Eastern Europe
CIS (former Soviet Union)
Middle East India (including Bangladesh, Bhutan, India, Myanmar, Nepal, Pakistan, Sri Lanka)
China (including China, Korea (DPR), Kampuchea, Laos, Mongolia, Vietnam)
East Asia South (Indonesia, Republic of Korea, Malaysia, Philippines, Thailand)

EIS computes the emissions of GHGs in 13 world regions (Tables IV-1 and IV-3). The energy-related emissions are based on the Targets Image Energy Regional (TIMER) simulation model (Figure IV-2). TIMER is a systems dynamics model with investment decisions in energy efficiency, electricity generation, and energy supply based on anticipated demand, relative costs or prices, and institutional and informational delays. The model uses five economic sectors. Technological change and fuel price dynamics influence energy intensity, fuel substitution, and the penetration of non-fossil options such as solar electricity and biomass-based fuels.

The objective of TES is to simulate global land-use and land-cover changes and their effect on emissions of GHGs and ozone precursors, and on carbon fluxes between the biosphere and the atmosphere (Figure IV-3). This subsystem can be used to:

  • Evaluate the effectiveness of land-use policies to control the build-up of GHGs.
  • Assess the land consequences of large-scale use of biofuels.
  • Evaluate the impact of climate change on global ecosystems and agriculture.
  • Investigate the effects of population, economic, and technological trends on changing global land cover.

More detailed information can be obtained by referring to the following web site:


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