Do model structures affect findings? Two energy consumption and CO2 emission scenarios for Brazil in 2010

The purpose of this paper is to compare some Brazilian energy and CO, emiss ion scenarios in order to verify how far model structures influence finding s and decisions. Two kinds of comparison were designed. The first one is be tween two scenarios drawn up for the same model, assessing the impact of en ergy and environmental policies in both quantitative and qualitative terms. The second comparison is based on the results of another model prepared in the early 1980s. Although the model structures are very different (optimisa tion versus simulation) the relative aggregate results for energy consumpti on and carbon dioxide emissions are relatively close. The differences al e due largely to structural changes in the Brazilian economy not anticipated at that time. However, when the model is broken down to display the specific needs, prior ities and constraints of Brazil, the results show appreciable qualitative d ifferences. This leads to the conclusion that an analysis of the functionin g of the economy is important for drawing up or adapting models. Consequent ly, it is believed that alternative energy policies designed to mitigate en vironmental impacts could be assessed more effectively. (C) 2001 Elsevier S cience Ltd. All rights reserved.