- -$36 - 



The process of running the models is not perfectly sequen- 

 tial. The ORNL and GISS models are coupled in an iterative 

 fashion for those analyses where the ORNL model is run. (This 

 is discussed below under the heading "Coupling the ORNL and GISS 

 Models.") Endnote 1 presents the rationale for coupling ORNL 

 and GISS models and compares results using the two basic analytical 

 approaches . 



MODEL DESCRIPTIONS 



Three models will be described: the IEA world energy model, 

 the ORNL carbon cycle model, and the GISS climate equation ocean 

 heat diffusion model. 

 The IEA Long-Term Global Model 



The IEA/ORAU model was developed by Jae Edmonds and John 

 Reilly at the Institute for Energy Analysis as an assessment 

 tool for policy analysis.^/ It provides a consistent represen- 

 tation of economic, demographic, technical, and policy factors 

 as they affect energy use and production and CO2 emissions. 



The global model is dissaggregated into nine regions (see 

 Figure B-2). Its time horizon is long-term — from 1975 to 

 2100 — with benchmark years 2000, 2025, 2050, and 2075. 

 Projections beyond 2050 have not been examined in detail for 

 reasonableness of parameters and model structure. Eleven 

 types of primary energy in six major categories are currently 

 considered (see Table B-l). In addition to the supply and demand 

 for energy by region and forecast period, the model also estimates 



