Publications

What do greenhouse gas scenarios tell us?

Manley, Dawn K.; Barter, Garrett B.; Askin, Amanda C.; Stephens, Thomas; Zhou, Yan; Ward, Jacob

In the coming decades, vehicle and fuel options and their supporting infrastructure must undergo significant transformations to achieve aggressive national targets for reducing petroleum consumption and lowering greenhouse gas (GHG) emissions. Vehicle electrification, advanced biofuels, natural gas, and hydrogen fuel cells are among the promising technology options that are being explored as future alternatives. A number of recent U.S. studies have examined how a mix of technology and policy options can contribute to the aggressive goals of 50- 80% reduction in petroleum consumption and 80% reduction in GHG emissions by 2050. These include reports issued by the National Petroleum Council, National Academies, and U.S. Department of Energy. While these studies all generally point to the need for a portfolio of technologies for the transportation sector, they do not draw the same set of conclusions for the portfolio mix. Moreover, they were commissioned for a variety of reasons, applied different modelling and analytical approaches in their assessments, and used a variety of assumptions in reaching their findings and recommendations. Using four recent major U. S. scenario analyses, this paper will illustrate several factors that can influence the interpretation of their results. Consideration of the underlying technology and policy assumptions, analytical approaches, and presentation of results can enable a more robust comparison across projections for the vehicle and fuel mix.