Issues in calculating airfreight emissions

There are three main challenges when trying to calculate the CO2 emissions from third party air freight:

1. Different aircraft types have different energy efficiencies, belly cargo might be different from dedicated cargo

2. Fuel consumption figures are generally regarded by airlines as highly sensitive

3. There is no standard methodology /reporting format for air freight CO2 data

There is also an ongoing debate whether to include the additional non-CO2 emissions or not. The Neutral Group's view is summarised below and a more detailed white paper report can be obtained by contacting us.

It is widely approved that due to the high altitude at which the emissions from aircraft occur the climatic impacts go beyond those that would occur from the emissions of carbon dioxide (CO2) alone. These impacts include the direct climate effects from CO2 and water vapor emissions, the indirect forcing on climate resulting from changes in the distributions and concentrations of ozone and methane as a consequence of aircraft nitrogen oxide (NOx) emissions, the direct effects (and indirect effects on clouds) from emitted aerosols and aerosol precursors, and the climate effects associated with contrails and cirrus cloud formation. However, there are large uncertainties in the present understanding of the magnitude of the total climate impacts due to aviation emissions. Further to these uncertainties, radiative forcing indices (i.e. multipliers) to the pure CO2 emissions should not be used as an emission metric to include the non-CO2 climate change impacts since it does not account for the different residence times of different forcing agents (IPPC, 2007), i.e. using a multiplier is a misapplication of science and it may attribute a larger fraction of climate change emissions to aircraft than is currently justifiable and, for fairness, any emission-based weighting of non-CO2 climate effects (beyond emissions of gases included within the Kyoto Protocol) should be applied to all sectors – not solely aviation (Forster et al. 2006). The Neutral Group therefore uses no multiplier for CO2 emissions from aircraft until:

1. Scientific and political consensus on an appropriate methodology has been achieved.

2. And the scientific understanding on this complex matter has improved to allow reasonable quantification – in all transport sectors notably.

The Neutral Group does however still acknowledge that the non-CO2 emissions may have, either directly or indirectly, a (significant) climate change impact.