RFI

co2balance uses a 'Radiative Forcing Index' (RFI) multiplier of 2 for all aviation calculations. At present there is good scientific evidence to suggest using an RFI value of 2 as a minimum. Future research may result in this value being increased to account for effects that we have limited understanding of at this time.

The RFI is a multiplier which allows for the environmental effects of all aircraft emissions at altitude to be considered. These effects are much greater than the CO2 which is released from burning the fossil fuels alone. NOx (Nitrogen Oxide) emissions at altitude produce O3 (Ozone), with a climatic impact similar in size to the CO2 emissions. The IPCC (1999) estimated the RFI for aviation in 1992 to be 2.7 with a range of 1.9 to 4.0. The TRADEOFF project has recently re-assessed aviation radiative forcing (Sausen et al., 2005) and the RFI for the year 2000 was calculated to be approximately 2.

Sausen, Robert; Isaksen, Ivar; Grewe, Volker; Hauglustaine, Didier; Lee, David S.; Myhre, Gunnar; Köhler, Marcus O.; Pitari, Giovanni; Schumann, Ulrich; Stordal, Frode; Zerefos, Christos, 2005: Aviation radiative forcing in 2000: an update on IPCC (1999). Meteorologische Zeitschrift, Volume 14, Number 4, August 2005, pp. 555-561(7)

Further information and details can be found at

"Changes in Atmospheric Constituents and in Radiative Forcing"
(Coordinating Lead Authors Piers Forester (UK), Venkatahalam Ramaswamy (USA)