Emissions Calculation by atmosfair
Since 2016, ETH Zurich has been working with its external partner atmosfair to calculate its air travel emissions based on the latest research on the climate impact of air travel.
The company atmosfair uses the external page VDR standard methodology to calculate greenhouse gas emissions from business travel. Taking into account several important factors and based on the current state of climate science, atmosfair's emissions calculator records the flight emissions as accurately as possible. Factors such as flight altitude, aircraft type or number of seats on board play an essential role, as do holding patterns, detours and taxiing on the ground. However, the calculation can never be completely accurate, as only the probable emission of a flight can be considered. Factors such as the actual occupancy of the flight or rerouting due to weather phenomena are not included in the calculation.
Furthermore, the exhaust gases produced and emitted during a flight consist of more pollutants than just carbon dioxide (CO2), which have additional, cumulative effects on the climate. Apart from the warming effect of CO2, there are so-called non-CO2 effects, such as contrails or the effect of nitrogen oxides (NOx) on local ozone concentrations (Fig. 1). Other constituents such as water vapor, soot, or sulfate compounds also have warming or partially cooling effects on the atmosphere, but largely cancel each other out.
In order to capture these complex non-CO2 effects generated during flights in a condensed way, researchers have introduced various metrics to compare these effects with the climate impact of pure CO2 emissions. The absolute global warming potential (AGWP) approach converts these other effects into CO2-equivalent (CO2eq) emissions under a 100-year time horizon.
Current research estimates that aviation at high altitudes has a cumulative warming effect (CO2 and non-CO2 effects) on the climate that is about three times larger than the effect caused by CO2 alone. atmosfair therefore applies this "factor 3" to all CO2 emissions at high altitudes to account for the climate impact of non-CO2 emissions.
To ensure comparability between years, ETH Zurich has been using the same climate factor (factor 2) since 2016, which was also used by atmosfair for the calculation of air travel emissions at that time.
Sources and related links
- external page call_made atmosfair: The impact of air travel on our climate
- external page call_made atmosfair Emissions Calculator
- external page call_made atmosfair Airline Index 2018
- external page call_made atmosfair: Offset a desired amount of CO?
- external page call_made EASA Report 2020
- external page call_made Lee et al. (2021): The contribution of global aviation to anthropogenic climate forcing for 2000 to 2018