Comparing individual components of a total climate impact is traditionally done in
terms of radiative forcing. However, the climate impact of transport systems includes contributions that are likely to imply climate sensitivity parameters distinctly different from the “reference value”
for a homogeneous CO2 perturbation. We propose to introduce efficacy factors for each component into the assessment. The way of proceeding is illustrated using aviation as an example, and prospects for evaluating the other transport system in the EU project QUANTIFY are given
