The pathology of Google's carbon-based flight metric

“A strange game. The only winning move is not to play.”

Google recently added a number of fairly odd features to their flight booking system that claims to help travelers learn how much carbon a given flight will release into the atmosphere (link).

But the numbers are misleading.

It's not exactly clear how they are computed, but even if they were correct on average, the irony of the feature is that a set of uncoordinated but climate-conscious consumers could end up increasing the aggregate amount of carbon for a given set of flights if they used these numbers as part of their decision-making process.

In fact - it's almost certainly true that price is a better predictor of the actual carbon emissions of a given route than the made-up Google metric. The cost of a flight is composed of a bunch of fixed costs which the airlines then try to make up on the margin by selling every seat on the plane. A full plane, broadly speaking, is the most carbon-friendly plane: and it's also the cheapest plane for everyone onboard.

Carbon emissions are obviously always lower for a direct flight assuming a full plane, but more direct flights between the set of airports would result in planes which are, on average, less full. There's some bin packing math to do here, but the basic premise is that while the naive calculation for me may imply that the direct flight from London to Austin only costs 731 kg of carbon dioxide, occupying one seat on both of the London to NYC and NYC to Austin flight may end up with fuller flights, thus reducing the per-capita cost of travel: both in carbon and dollar terms.

If consumers were to use this tool, therefore, the result could actually be to push airlines away from more efficient hub-spoke routes towards direct flights with lower utilization.

Of course, it's hard for me to actually believes that anyone actually think this matters: once you've chosen to fly to London, you've basically made the call that you're going to use a tremendous amount of carbon dioxide no matter what route you pick. And implying that the choice of flying direct is 20% better for the environment is just lazy - if you can book the flight, the planes are already taking off with or without you.

Climate change is not a problem that will be fixed by individual action: if we want to fix this problem, we need to pursue unpopular policies to increase the cost of carbon. As a consumer, trying to do multi-variate optimization for every choice is an exhausting way to make decisions; it's why having the almighty dollar, rather than a cryptocoin for every commodity, is the way we evolved out of a primitive economy into one based on the free exchange of goods and services.

Which leads me to the question: why did anyone at Google green-light this project?

The most cynical answer: it lets rich people (like Google employees) who can afford direct flights feel good about their ability to pay more money for convenience by giving them a hedonic boost when they book "carbon-friendly" direct flights (which again, they were going to do anyway, because they are actually paying for convenience).