Models of the global energy system can help shed light on the competition and complementarities among technologies and energy systems both in the presence and absence of actions to affect the concentration of greenhouse gases. This paper explores the role of modeling in the analysis of technology deployment in addressing climate change. It examines the competition among technologies in a variety of markets, and explores conditions under which new markets, such as for hydrogen and carbon disposal, or modern commercial biomass, could emerge. Carbon capture and disposal technologies are shown to have the potential to play a central role in controlling the cost of stabilizing the concentration of greenhouse gases, the goal of the UN Framework Convention on Climate Change. (C) 2004 Published by Elsevier Ltd.