When Google launched a carbon emissions tool for its flight tracker last fall, allowing consumers to see the individual emissions created by each flight they were browsing, it received widespread attention and praise from industry leaders and climate scientists alike. But last month the tech giant quietly shifted the algorithm to exclude a crucial component of the overall greenhouse gas impact of air travel — meaning that emissions data on the flights it lists now are much lower than they were before.
“Google has airbrushed a huge chunk of the aviation industry’s climate impacts from its pages,” Dr Doug Parr, the chief scientist and policy director of Greenpeace UK, told the BBC.
The change, Google said in a public Github post from last month, was made after consultations with the tech giant’s “academic and industry partners.” In the Github post, Google said it has decided to only calculate carbon dioxide emissions from flights, rather than the cumulative effect of all greenhouse gasses — known as CO2E, or “carbon dioxide equivalents,” in climate-speak. In particular, Google has decided to temporarily do away with calculations related to contrails, the clouds that form behind planes, that can have a big impact on flight emissions.
While carbon dioxide makes up the bulk of greenhouse gas emissions from flights, the exclusion of contrails — which form after the water vapour in jet fuel freezes, creating the clouds that streak the sky following flights — is a curious one. The clouds produced by frozen jet vapour can actually produce a temporary greenhouse gas effect by trapping heat in the atmosphere.
The warming effect of individual contrails is pretty short-term, since the clouds disappear within a few hours. But given the thousands of flights that are in the sky at any given moment — the U.S.’s Federal Aviation Administration alone handles more than 45,000 flights each day — those “temporary” warming clouds can cause real damage.
Google says that calculating contrail impacts on individual flights is tricky, and while it’s worth doing, they want to develop a mechanism to make more accurate predictions for specific flights. “We strongly believe that non-CO2 effects should be included in the model, but not at the expense of accuracy for individual flight estimates,” a Google spokesperson told Earther in an email. “To address this issue, we’re working closely with leading academics on soon-to-be-published research to better understand how the impact of contrails varies based on critical factors like time of day and region, which will in turn help us more accurately reflect that information to consumers.”
While accuracy might not be easy, some of the findings on the overall impacts are scary: A 2011 analysis concluded that the warming impact of contrails could be greater than the impact from plane fuel itself. Another study predicted contrails’ warming effect could triple by 2050, as air traffic continues to grow.
By making changes to the carbon emissions calculation, Google might radically lower its estimates for some flights. The BBC calculated that before the shift in the equation, the tool may have shown that a flight from Seattle to Paris emits 1,070 kilograms of carbon dioxide equivalent (kgCO2e) per person; after the shift, it’s down to just 521 kgCO2e.
A Google spokesperson said in a phone interview that the goal of the tool is to provide carbon emissions to customers who may want to compare similar flights — for instance, providing the ability to choose between leaving for vacation on a flight from one airport near New York at one time of day versus a different airport at another time of day — rather than just viewing how much CO2 you’re going to be emitting on that vacation in general. The spokesperson said that internal research showed that customers don’t necessarily respond to the actual numerical of the CO2 involved, but rather just to the comparison between products, which is still maintained even with the contrail equation taken out. The spokesperson emphasised that in addition to speaking to “industry partners” — like the airline industry as well as other online travel platforms — researchers at MIT and the Imperial College of London are also helping to adjust the equation. There’s no current timeline for reintegrating contrails back into the tool.
It’s laudable that Google is trying for real accuracy here. But the whole episode raises questions about the purpose and clarity of individual tools like these. There’s no note on the tool about the changes made last month to the reading, or a warning that the actual warming impact could be twice as high as what the tool actually shows. Even if Google’s tool is mostly for shopping comparisons as the company says, a consumer should be told that the numbers they’re looking at may be much higher. And given the substantial carbon reductions the world needs over the next decade, it is arguably even more important now to consider short-term greenhouse effects like contrails. There’s an argument to be made for overestimating emissions of flights, rather than underestimating.
We’re constantly being told by private companies that changing our individual actions can be as effective at fighting climate change as widespread, systemic changes. It’s worrisome when the airline industry — which only stands to lose if consumers see the massive ecological impact of flying — get to help decide how that data is displayed to the public.
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