How we calculate flight CO2 offsets

METHODOLOGY

We calculate aviation emission footprints using a methodology that is consistent with the following:
- ISO14064-1 carbon standard
- International Carbon Reduction and Offset Alliance (ICROA)
- The most recent NZ Ministry for the Environment Guidelines for Voluntary GHG Reporting

This includes using the latest emission factors and methodologies from the NZ Ministry for the Environment (MFE), and the UK equivalent (DEFRA). This includes an 8% Great Circle Flight Distance Uplift Factor accounting for curvature of the earth, delays, indirect routes, circling etc. We also add a 1% margin for conservativeness (to account for uncertainty, extra baggage etc.). We also give customers the option to include or exclude accounting for Radiative Forcing (RF).


RADIATIVE FORCING (RF)

What Is Radiative Forcing?

Radiative forcing refers to the non-CO2e impacts of aviation emissions on global warming (e.g. NOx, water vapour, contrails) (impacts in addition to the CO2e gases). Accounting for radiative forcing is a more conservative approach to calculating aviation emissions footprints, compared with when RF is excluded.

Does MFE Require Radiative Forcing To Be Included in Voluntary Emissions Calculations?

No. Neither the NZ Ministry for the Environment (MFE) nor the UK equivalent (DEFRA) require voluntary GHG reporting to account for radiative forcing for aviation emissions. This is due to the current scientific uncertainty associated with the methodology for calculating radiative forcing. 

Do Voluntary Carbon Offset Suppliers Require Radiative Forcing To Be Included in Aviation Emission Calculations?

Some voluntary carbon offset suppliers in NZ and internationally make it mandatory to include radiative forcing in the calculation of aviation emission GHG footprints. Others do not include it.

When calculating the effects of radiative forcing, Ekos uses the methodology and multiplier recommended by the European Assessment of Transport Impacts on Climate Change and Ozone Depletion (ATTICA). This applies the ATTICA recommended multiplier of 1.89 to the appropriate emission factors for aviation flight distances.