Components of IMAGE 2.4

Components

Base year, scale and spatial resolution.

The temporal scale in IMAGE 2.4 is year-based (as for all other model components), although climate parameters (precipitation and temperature) are generated on a monthly basis through pattern scaling. The number of world regions has been extended from 17 to 24 (plus Greenland and Antarctica) (and to 26 in the TIMER model) to reduce scale problems occurring in previous IMAGE versions. Historical data for the 1765-2000 period are used to initialise the carbon cycle and climate system, while data for 1970-2000 are used to calibrate the energy system (TIMER model) and the agricultural system. IMAGE 2.4 simulations generally cover the 1970-2050 period and for climate scenarios, often the period 1970-2100. Simulations are made on the basis of scenario assumptions on, for example, demography, food and energy consumption and technology and trade. Although IMAGE 2.4 is global in application, it performs many of its calculations either on a high-resolution terrestrial 0.5 by 0.5 degree grid (land use and land cover and associated emissions) or for the 24 world regions in IMAGE 2.4 (energy, trade and emissions).

Economy and demographics

The exogenous source for macro-economic drivers depends on the study in which IMAGE 2.4 is applied. Population projections are taken primarily from authoritative exogenous sources such as the UN or IIASA, but may also be adopted from the in-house demographic model, PHOENIX (Hilderink, 2001).
New elements: 

• In IMAGE 2.4, grid-based population dynamics have been improved by introducing a new downscaling algorithm. Population within a grid cell is calculated with a proportional method using available country-specific data combined with the trends on the world regionlevel, as determined by PHOENIX. This approach allows for simulating shifts in population within IMAGE regions.           

Energy demand and supply

In the TIMER model, aggregated economic indicators like GDP, household consumption and value added in industry, services and agriculture are used to estimate the demand for energy services. Energy supply chains with substantial technological detail are then selected on the basis of relative costs for meeting the resulting final energy demand after autonomous and price-induced energy savings. Market shares for energy resources and technologies are calculated via a multinomial logit distribution function (de Vries et al., 2001). TIMER includes explicit treatment of traditional biofuels, vintages of capital stock, learning-by-doing (i.e. technologies improve as their installed capacity is build-up) and resource depletion (driving up costs for extraction of exhaustible energy resources). It generates primary and final energy consumption by energy type, sector and region; capacity build-up and utilisation; cost indicators, and greenhouse gas and other emissions.
New elements:

• Important new elements introduced in the TIMER 2.0 model (part of IMAGE 2.4) are hydrogen production and more detailed descriptions of the electric power system and renewable energy, including bioenergy.           

Agricultural demand and trade

The agricultural demand model of IMAGE 2.2 has been replaced by a coupling to the global trade analysis project (GTAP) model.
New elements: 

• GTAP calculates consumption and trade of agricultural products by taking regional and world market prices into account, which are calculated explicitly from production functions including capital, labour and land prices. In return, IMAGE 2.4 provides land-supply curves, yields and yield changes, that result from climate change and expansion of agriculture to less productive areas, and simulates the geographically explicit environmental impacts. This iterative coupling between GTAP and IMAGE allows assessment of the economic and environmental consequences of specific trade policies.           

Land use

One of the most striking parts of IMAGE 2.4 is the geographically explicit land-use modelling, considering both cropping and livestock systems on the basis of agricultural demand and demand for energy crops. The rule-based allocation accounts for crop productivity (Agro-Ecological Zones approach; (FAO, 1978-1981), and other suitability factors like proximity to existing agricultural land and water bodies. Changes in natural vegetation cover on undisturbed or abandoned land are simulated in IMAGE 2.4 on the basis of a static natural vegetation model (Prentice et al., 1992).
New elements:

• The land-cover type "energy crops" is now included in IMAGE 2.4. A more detailed description of animal production systems has been introduced in IMAGE 2.4 to portray the spatial variability in grazing systems. Also addressed is rapid development of intensive ruminant production on managed grassland and the rapidly increasing use of various feedstuffs. Moreover, a new initial land-use map for 1970 is incorporated on the basis of satellite observations combined with statistical information.           

Carbon cycle

The consequences of these land-use and land-cover changes for the carbon cycle are simulated by a geographically explicit terrestrial carbon cycle model. If agricultural land is abandoned, it is assumed to revert gradually to its more natural state, with implications for the carbon stock. The carbon cycle model, implemented in the IMAGE framework since version 2.0, has been subjected to a thorough evaluation, which showed that the model is suitable for simulating global and regional carbon pools and fluxes. The model accounts for important feedback mechanisms related to changing climate, CO₂ concentrations and land use.
New elements:

• An addition to the C cycle model is the evaluation of the potential for carbon sequestration in natural vegetation and carbon plantations.           

Nitrogen cycle

In contrast to IMAGE 2.4, IMAGE 2.2 and 2.3 did not include tools to assess the impact of ever-increasing nutrient loads in agricultural systems and aquatic ecosystems.
New elements: 

• IMAGE 2.4 includes a new module to assess the consequences of the changing population, economy, land use and technological development for surface-nutrient balances and reactive nitrogen emissions from point sources and non-point sources. These surface balances form the basis for describing the major fluxes in the global and regional nitrogen cycle, as well as the effects on water and air quality. Processes accounted for in this module are human emissions, wastewater treatment, surface nitrogen and phosphorous balances for terrestrial systems, ammonia emissions, denitrification and N₂O and NO emissions from soils, nitrate leaching, and transport and retention of nitrogen in groundwater and surface water. In order to derive spatially explicit scenarios, tools were developed to translate regional or country-specific information to grid-specific input parameters.           

Atmosphere-Ocean system 

Emissions from the energy system and emissions due to land-use changes  determine the composition of the atmosphere. IMAGE 2.4 uses the Atmosphere–Ocean System model developed for IMAGE 2.2.

Not strictly coupled modules

Biodiversity

In addition to these environmental impacts of global change calculated within the core biophysical modules, results are also used as input to drive impact models in the broader IMAGE 2.4 framework such as the biodiversity model, GLOBIO 3. GLOBIO can be used to assess the impacts of climate and land-use change, infrastructure and nitrogen deposition on biodiversity and ecosystems. Likely effects of scenario assumptions or political interventions are estimated by calculating trends in mean species abundance.

• to GLOBIO website

Climate policies

IMAGE results are also used for the evaluation of climate policies in conjunction with the policy decision-support model FAIR . FAIR is widely used to assess the environmental and abatement cost implications of international regimes for the differentiation of future emission reductions of greenhouse gases. The model links long-term climate targets and global reduction objectives with regional emission allowances and abatement costs, accounting for the Kyoto Mechanisms.

References

Bouwman AF ; Kram T ; Klein Goldewijk K (eds) (2006). Integrated modelling of global environmental change. An overview of IMAGE 2.4. Netherlands Environmental Assessment Agency

• to the publication

Hilderink, HBM, 2000. World population in transition : an integrated regional modelling framework. Amsterdam, Thela Thesis / Rozenberg. 

• to the thesis 

De Vries B, Van Vuuren D, Den Elzen M, Janssen M, 2001. The Targets Image Energy Regional (TIMER) Model. Technical Documentation,  Netherlands Environmental Assessment Agency (MNP). Report no. 461502024

• to  the publication  

Agro-Ecological Zones approach. FAO, 1978-1981

Prentice I.C., Cramer W., Harrison S.P.,Leemans R., Monserud R.A. and Solomon A.M. (1992) A global biome model based on plant physiology and dominance, soil properties and climate. Journal of Biogeography, 19:177-134.