When author Jack Miles calculated the carbon cost of his flight from Los Angeles to Morocco, he took into account the distance, and the layover. And then he took that number, and had to literally double it:

My seats alone on the round-trip flights from Los Angeles to Casablanca (with a layover in Paris) helped emit about 8,400 pounds of carbon dioxide, prorated, into the atmosphere.

Double that because my wife accompanied me.

In sum, our seats alone on the planes to and from Morocco helped unload about 16,800 pounds of carbon dioxide. And this, of course, was just a small fraction of the emissions cost of the flight as a whole.

Jack Miles, “For the love of Earth, stop traveling”

The upshot: the climate impact of their flight would have been halved if Miles’ wife had stayed home.

Maybe there’s something to be said for solo travel?

If you can’t bring the number of flyers in your party down to zero, maybe it’s enough to just reduce it. This isn’t a facetious point. After all, when Sarah Clayton of AirportWatch chose to travel by train, while her husband flew, they cut their collective aviation emissions by half.

As a bonus, the fact that personal aviation emissions grow linearly with the number of people in a party means that curbing a plane journey for an entire family can have significantly more impact than just dropping a single passenger. Take the story of Swedish lawyer Pia Bjorstrand, for example, who cut 8 passenger-flights when she, her husband, and their two sons skipped flying to do a vacation by train. Or Elisa Vertue and James Wilson, a family from London with two children, who also cut 8 passenger-flights when their family of four skipped a flight to Italy.