Google, IATA, ICAO misrepresent the climate impact of flying

“Google ‘airbrushes’ out emissions from flying,” BBC revealed last week. Let me explain what this story is all about – and reveal that Google is not the only industry big boy to knowingly ignore some of the important flight-related emissions in its climate footprint calculator.
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Written by Jussi Ahola
CEO and Co-Founder at Oncarbon
August 29, 2022

In October 2021, Google added a new feature to its Google Flights service that shows users the climate impact of the flights they are browsing. At the time, Google stated that this way “buyers can consider their environmental footprint in the same way they consider price and duration.”

The move was announced as part of the tech giant’s larger efforts to combat climate change. A few weeks earlier, Google had joined the Travalyst Coalition, a group of travel giants like,, Visa, and others, committed to making sustainability the standard in the travel industry. The plan was for the other Travalyst members to also adopt the Google-developed model and start showing flight emissions numbers in their booking sites (we are still waiting for it).

In July 2022, Google decided to make a massive change to its calculation model, and the story was picked up by BBC, Business Insider, Euronews and several other major media outlets.

Backstory: In June, we were reviewing the methodology that Google uses for their emissions calculations, and were unhappy with the way their model accounted for non-CO2 warming effects of jet flights: these effects include NOx, water vapour, contrails, and some other effects.

Although the exact magnitude of these effects depends heavily on the exact circumstances of an individual jet flight and involve uncertainty, some latest research on the topic suggest multiplying the direct CO2 emissions, on aggregate, by a factor of 3.0 to arrive at the true warming potential of a jet flight (GWP100)1. This multiplier is often referred to as the Radiative Forcing Index (RFI).

The multiplier that Google was using back in June was 1.61, leading their model to wildly underestimate the true warming effect of flights and to millions of consumers being given misleading information of the true environmental cost of flying.

We asked Google about this back in June, inquiring why the low RFI?

Google’s reaction to this? They removed the RFI from their model entirely – leading them to underestimate the true warming effect of flights by even more!

After BBC’s coverage of this story, scientists are confirming our concerns. “Google has airbrushed a huge chunk of the aviation industry’s climate impacts from its pages,” said Dr. Doug Parr, Greenpeace’s chief scientist, in reaction to the BBC’s article. Professor David Lee of Manchester Metropolitan University, the author of the most comprehensive scientific assessment of the contribution to global warming, added: “The global climate impact of aviation is now significantly underestimated”.

Yes – the global climate impact of aviation has been underestimated for years, and by many significant industry players. But why are those non-CO2 emissions so important to make such a fuss around them? Let me briefly explain.

CO2 emissions are just the tip of the iceberg

When an aircraft engine burns fossil fuels, it emits various gasses. The best known is CO2, but it’s not the only one. Other gasses include nitrogen oxides (NOx), water vapor, carbon monoxide (that bonds with oxygen to form CO2), and other atmospheric particulates such as soot and sulfate aerosols.

The catch is that an airplane flying at high altitude causes more warming from these gasses, vapors, and aerosols than if the same amounts were emitted at sea level. The warming potential of these non-CO2 effects is communicated as carbon dioxide equivalents (CO2e). CO2e is a yardstick that compares the warming potential of non-CO2 effects to the warming potential of CO2: what is the amount of CO2 that would have the same warming potential as these non-CO2 effects have?

Because there hasn’t been a universal agreement on the RFI value that everyone should use to cover for these non-CO2 effects, different flight emissions calculators use different numbers. Some, like Google, omit the effect entirely.

To us, the most comprehensive recent study on the topic is by David S. Lee, et. al, published in the journal Atmospheric Environment 2, which concludes that a realistic RFI value for today’s flights, on aggregate, is 3.0.

This means that the total global warming caused by aviation is three times that of CO2 alone, and that CO2 emissions are just a tip of the iceberg. On average, the CO2 impact of a flight must be tripled to account for its total climate impact.

Google is not the only one that ignores non-CO2 emissions

Why doesn’t Google include non-CO2 emissions in its calculations? The company states that it “believes in including non-CO2 effects in the model over the long term, but the details of how and when to include these factors will require further input from our stakeholders as part of a governance model that is in development. Google is committed to providing consumers with the most accurate information as they make informed choices about their travel options.”

Given the removal of non-CO2 effects from their calculations, we cannot agree with what they are saying. Google’s numbers wildly underestimate the environmental impact of flying and mislead millions of consumers.

However, Google is not alone in ignoring non-CO2 effects in its methodology. IATA (International Air Transport Association) and ICAO (International Civil Aviation Organization) also do not consider non-CO2 emissions in their calculation methodologies. In its recently published “Recommended Practice of Passenger CO2 Calculation Methodology”3 IATA states that “the use of the Radiative Forcing Index (RFI) is not recommended as long as scientific uncertainties exist about the exact effects and as long as consensus has not been reached in the global scientific community on the value(s) to be used.” ICAO stated that it “will only adopt a multiplier if the scientific community reaches a general agreement on this issue.”

Sure, uncertainties on the exact, down-to-two-decimal-places RFI exist. However, there is zero uncertainty that the calculation methodologies that Google, IATA, and ICAO misrepresent the actual climate effects of flying.

How is the climate footprint of a flight calculated?

As Oncarbon, we would like to emphasize that the lack of agreement on radiative forcing does not mean that there is no additional warming effect. We have a methodology for flight emissions using the latest scientific research and the RFI value of 3.0. This is why our calculator shows very different numbers than the one provided by Google.

You can see this in the example of a flight from London Heathrow to New York JFK with American Airlines on a Boeing 777 300ER.

According to Google, one passenger in economy class on this flight will account for 392 kg of CO2.

The ICAO calculator indicates that the value will be 315.3 kg of CO2 per passenger in economy class.

Our calculations at Oncarbon for this distance (5,665 km) and the number of seats on the plane (304) show that one seat accounts for 1396 kg CO2e for the same itinerary, plane, and class.

Carbon footprint of a flight London-New York
Emissions according to flight phases.

This is a significant difference – and for good reason, we believe. If you want to read more about our approach to emissions modelling, make sure to see our methodology.

Let passengers know the real impact of flying

Google is a tech giant, we are a five-person startup – and we believe in transparency and integrity. I believe that only an honest account of flight emissions can lead to a positive change in consumer behavior and thus to a reduction in emissions from flying. With greenwashing at its best, consumers often don’t know which travel products are the lowest-emitting ones, and they find it difficult to trust airlines that provide their own numbers, without third-party verification.

We know that what we communicate might not be the most convenient information for airlines and flight resellers – but with emissions and global temperatures rising, it’s pointless to pretend that flying doesn’t harm the environment, and that we can enjoy flying without guilt. The uncomfortable truth is more valuable than a reassuring lie: we all need to acknowledge that flying is doing significant damage to our planet, and that we will not be able to talk about "carbon-neutral" or "sustainable" flights for some time yet.

Passengers have a right to know the impact of their flight on the climate. It’s really time to tell them the truth.

Cover photo: USGS/Unsplash.

Picture of Jussi Ahola
Jussi Ahola
Building Oncarbon by day, sailing on an old 22′ boat by night. CEO and Co-Founder at Oncarbon.