"Flight booking platforms are giving customers a new number to think about when they buy a plane ticket: the expected greenhouse gas emissions of their trip.

If you’ve searched for plane tickets on Google Flights in the past two years, you’ve probably seen a little green number that compares each route’s climate impact. Google began predicting flight emissions in 2021, using data about flight schedules, airplane models and how full a flight is expected to be to come up with an estimate for each passenger’s carbon footprint.

Lately, other platforms, including Expedia and Booking.com, have started using the same algorithm, called the Travel Impact Model (TIM), to tell customers whether their itinerary emits more or less carbon than usual.

But what, exactly, are these little green numbers — and how should an eco-conscious traveler take them into account when picking out flights? We asked the group that manages the model and a pair of economists what you should do with your emissions estimate."

Nicolás Rivero reports for the Washington Post March 15, 2024. [2]