Analysing international shipping and aviation emission projections

Improving the representation of international transport in integrated assessment models is needed

Integrated Assessment Models (IAMs) are often used to develop and assess mitigation pathways in which greenhouse gas emissions are reduced to limit warming to a specific temperature, at the lowest overall cost. At the moment, international aviation and shipping are underrepresented in most IAMs. Improving the representation of international transport would enable providing better insight into its potential contribution to global mitigation. This is the main finding from this assessment study, based on a questionnaire and interviews with several IAM teams, an analysis of published emission projections, and a comparison between IAM projections and projections of non-IAMs (mainly sectoral models) that focus on the transport sector. A key reason for this underrepresentation is that data on both domestic and international transport activities and energy use are not easily available.

A systematic analysis of data on historical activity, energy use, and mitigation potential is needed

This report recommends systematic analysis of data on historical activity, energy use, and mitigation potential to improve IAM representation of the international aviation and shipping sectors. Specific recommendations for teams wishing to improve the representation of these sectors are:

• Distinguish between aviation and shipping and between domestic and international;
• Distinguish between national and international transport emissions;
• Incorporate fuels, efficiency standards, and energy or transport demand levers.

Sectoral models can be used to help improve the representation of the demand and activity data on international aviation and shipping and technological mitigation options in IAMs. Sectoral models could also be soft-linked to IAMs.