Google will update flight emissions calculations in its Travel Impact Model

Google will make updates to its Travel Impact Model (TIM), a tool it created in 2022 to calculate flight emissions at the individual passenger level.

The changes were announced by the International Council on Clean Transportation (ICCT), which serves as the secretariat of an independent advisory committee created last summer to oversee future updates to the TIM and to ensure it provides accurate, transparent and consistent emissions data.

Google’s TIM powers the emissions estimates on Google Flights and, since April 2022, has been used by other members of the Travalyst coalition, including Booking.com, Expedia and Skyscanner.

The ICCT said the updates are intended to make the emissions model “more fully reflect the environmental impact of aviation and help people make more sustainable choices when planning air travel.”

The updates, which will soon be reflected in emissions estimates on any platforms using the TIM, include:

• Taking into account all six Kyoto greenhouse gasses. The AC agreed to expand the scope of the TIM to include all six Kyoto gases, especially CO2, CH4 and N2O. This update means that the model will be able to accommodate changes that include climate effects beyond just CO2 emissions, and going forward the model outputs will be labeled as “CO2 equivalent.”
• Including well-to-tank emissions by default. Following the decision to account for all six Kyoto gases, the AC decided that the TIM should be expanded to reflect the climate effects resulting from the production and transportation of aviation fuels, commonly referred to as well-to-tank (WTT) emissions. … This update sets the stage for crediting airlines that introduce new technologies to reduce greenhouse gas emissions, notably sustainable aviation fuel.
• Integrating belly cargo. The AC determined that the emissions resulting from a given flight should be apportioned over both passengers and any belly cargo being transported. … This decision, which reflects the mass of passenger service equipment, is an interim solution until international standards can be aligned.

“These changes are an important step in making the TIM more comprehensive and future-proof,” said Dan Rutherford, the ICCT’s aviation director and head of the TIM secretariat. “The Advisory Committee will continue work in 2024 to provide even more consistent and transparent emissions estimates to travelers.” 

Along with these changes, the AC has agreed to prioritize research on contrails, looking at impacts by time, region and airline and how to communicate that to consumers.

In 2022, a BBC report accused Google of intentionally minimizing the reported environmental impact of flights because its calculations were not comprehensive and specifically did not include contrail impacts.