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Principles and Methods

Since 2006, ETH Zurich has been monitoring the greenhouse gas emissions from air travel by its employees, students and guests.

As the basis for the Air Travel Project, a Downloadframework concept (PDF, 286 KB) was developed in 2016 by the company EcoExistence, which provided the ideas for the target definitions and the compilation of reduction pathways. It also laid the foundation for the development of the participatory process between the departments. In parallel, Downloaddefinitions (PDF, 177 KB) around the reduction of air travel emissions at ETH were developed by the former ETH Zurich Mobility Platform.

For the years 2006 to 2016, the company EarthEffect was assigned to calculate the emissions from business travel (air travel, car travel, train travel) at ETH Zurich based on the existing travel costs. All business trips of ETH members and guests for which the travel costs were covered by ETH Zurich were recorded. At this time, student travel was not yet included. This Downloadmethod description (PDF, 192 KB) and this Downloadsummary (PDF, 128 KB) by EarthEffect on greenhouse gas emissions from business travel at ETH Zurich provide more detailed information.

For the years 2016 to 2018, the company Infras took over the calculation of emissions from business trips at ETH Zurich. Infras applied the same method as EarthEffect but with a small correction, which is described in this Downloadsummary (PDF, 293 KB). Infras wrote two further documents describing the procedure and methods used to record greenhouse gas emissions from flights and the consideration of non-CO2 climate contributions from air travel at ETH Zurich.

At the same time, the company external pageatmosfair was commissioned to calculate the emissions with the standard VDR methodology used today, based on the actual flight information such as flight number, flight date, type of aircraft, etc. The atmosfair method is considered the most accurate of the three methods and is therefore used exclusively for the calculation of ETH flight emissions since 2016. Further information on the calculation of emissions by atmosfair can be found on the page Emissions Calculation by atmosfair in the Data Stewardship section.

To make the data comparable and consistent, the EarthEffect and Infras data from 2006 to 2016 were corrected retroactively and aligned with the atmosfair data. At the same time, estimates were made for student flights so they could also be retroactively amended for the same time period. This Downloadreport (PDF, 728 KB) from 2021 by external pageIselin Medhaug explains the alignment procedure (Fig. 1). Based on the atmosfair data from 2016 to 2019, Iselin Medhaug wrote another Downloadreport (PDF, 3.5 MB) that provides a detailed analysis of the flight behavior and emission trends at the ETH department level.

Figure from Medhaug (2021)
Fig. 1: The original EarthEffect emissions (magenta line), together with the scaled emissions from employee and guest flights (light magenta) and student flights (light blue), and the atmosfair emissions for employees and guests (dark blue) and students (cyan) for the overlap period of the two time series (from Medhaug, 2021; Fig. 3).

Additional documents

EcoExistence:

EarthEffect:

Infras:

Iselin Medhaug:

Former Mobility Platform, ETH Zurich:

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