Does a flight between Paris and Seattle emit 500, 1000 or 1500 kg of CO2 equivalent? A legitimate question when Google decided to review its calculation method, sometimes halving the estimates offered to Internet users.
Google is strong. Very strong. Especially when it comes time to address a major environmental issue: greenhouse gas emissions from the aviation sector. As proof, with a wave of a magic wand, the online search giant has “erased much of the impact of the aviation industry on the climate”regrets Doug Parr, scientific director of Greenpeace.
Don’t be reassured though. No matter what Google thinks, airplanes continue to emit the same amounts of CO2. The search engine has just decided to modify the method of calculating the carbon emissions of its Google Flights service, going so far as to halve the estimates presented to Internet users. Why did Google do such a thing? In order to better reflect the reality of carbon emissions, after consulting “its partners in the industry”assures the American giant.
From single to double
We can obviously be alarmed to see the world’s leading search engine, which processes 9 out of 10 queries in the United States and Europe, minimizing the impact of the plane in the midst of the climate crisis. Especially since its Flights service is widely highlighted in air travel searches carried out on the engine, and its figures are used by a whole section of the industry, from Skyscanner to Booking. But is Doug Parr right to be offended? Because the crucial question in this case is to know if the new calculation method is really more realistic than the old one, as Google seems to claim. To find out, let’s try some comparisons.
Of course, we are talking about estimates here and not the actual emissions from the flights. For a flight connecting Seattle to Paris, Google Flights indicated emissions per passenger of around 1070 kg of CO2 before the change in its methodology. Today, users of the service see an estimate of 521 kg of CO2 per passenger. From single to double. One of two things: either Google Flights strongly overestimated emissions before, or it strongly underestimates them today. What do other recognized tools for estimating the impact of air transport say?
Very disparate information depending on the simulators
The French government’s tool, set up with Ademe (ecological transition agency), indicates emissions in CO2 equivalent of around 666 (!) kg for a Seattle / Paris flight. This is, to within 1 kg, the estimate provided per passenger by Air France for one of its planes connecting the airports of Tacoma and Charles de Gaulle. We could therefore say that even if Google went a little too far in reducing the estimated emissions for this flight, the new figure is ultimately closer to “reality” and is similar to that provided by other calculators of the same kind.
Except that by digging a little more, and using other simulators such as that of the GoodPlanet foundation, we obtain completely different estimates, of the order of 1450 kg to travel the 8042 km which separate the two cities. In this case, even the old calculation method of Google Flights was quite far off the mark!
By analyzing the methodologies of the different simulators, we find the explanation: the result of the estimates depends strongly on whether or not “radiative forcing” is taken into account. As CarbonFootprint explains: “Aircraft carbon emissions at high altitudes worsen global warming. Check this box to multiply aircraft emissions by DEFRA’s recommended radiative forcing factor of 1.891”. And inevitably, taking into account this factor on long-haul flights, it is no longer the same thing.
We are talking here about the role of contrails which trap the heat emitted from the Earth and have a strong effect on the climate. 2% of flights would be responsible for 80% of contrails, and if aviation generates 2% of CO2 emissions, it would actually be the source of 3.5% of the warming caused by human activity if we incorporates its broader direct impacts.
The influence of aviation seriously underestimated
Google, which is pleased to inform Internet users to help them operate “more sustainable travel choices”, would therefore be on the wrong track, as confirmed by experts on the subject interviewed by the BBC. They indicate that since July, Google has decided to exclude from its estimates all the impacts of aviation on global warming with the exception of CO2. David Lee, professor at Manchester Metropolitan University, one of the most quoted authors on the consequences of air transport in terms of global warming, therefore regrets that the figures displayed now represent half of the real impacts of flights, and “greatly underestimate the influence of aviation on the climate”.
Questioned by the BBC, Google recognizes without difficulty that all the effects of aviation, even those which are not directly attributable to CO2, should be integrated into its calculations, even if discussions must still be carried out in this direction internally. “The industry has hidden this problem for decades…Google should show customers the non-CO2 effects for every flight, as the European Parliament has proposed to do”add the English activists of the association Transport and Environment.
The stakes are high because, more than ever, everyone must be able — in complete transparency and using reliable tools — to estimate the impacts of their activities in order to be better able to reduce them. Moreover, understated figures should not be used to exempt aviation from the efforts to be made in the fight against global warming, or to reduce the pressure placed on this industry for this purpose.