During the past decade, several macroeconomic studies on the potentials of information and communication technology (ICT) to reduce greenhouse gas (GHG) emissions have been published. The mitigation potentials identified in them vary to a high degree, mainly because they are not consistently defined and diverse methodologies are applied. The characteristics of ICT—exceptional dynamics of innovation and diffusion, social embedment and cross-sector application, diverse and complex impact patterns—are a challenge for macroeconomic studies that quantify ICT impacts on GHG emissions. This article first reviews principal macroeconomic studies on ICT and GHG emissions. In the second part, we reconsider our own study on this topic and present an in-depth scenario analysis of the future impacts of ICT applications on GHG emissions. We conclude that forthcoming macroeconomic studies could strengthen the state of the art in environmental ICT impact modeling (1) by accounting for the dynamics of new ICT applications and their first-, second-, and third-order effects on a global scale, (2) by reflecting the error margins resulting from data uncertainty in the final results, and (3) by using scenario techniques to explore future uncertainty and its impacts on the results.