Low carbon flights on the internet

If you travel a lot, you’re probably used to visiting airline web sites and being asked whether you want to see your flights sorted by **price** or **schedule**. How would you like to sort by **carbon**?

Until recently, only experts in aviation emissions could track down this information. But now the public can find comparative data using TerraPass’ new aviation calculator. The results can help you choose the flight with the lowest climate impact. Here’s what I found during a check of popular U.S. air routes:

Route Airline Pounds of CO2*
JFK to LAX Virgin America 1,390
  Delta 1,456
  American 1,586
  United 2,070
SFO to JFK Delta 1,425
  Virgin America 1,450
  JetBlue 1,462
  Alaska 1,496
  American 1,530
  United 2,158
DCA to LGA US Airways 260
  United 304
  Delta 350
  American 816
ATL to ORD Delta 543
  United 611
  US Airways 614
  American 708
LAX to SFO Virgin America 344
  United 351
  American 397
  Southwest 406
  Alaska 420
  Delta 798

\* Per passenger, round-trip flight, economy class

The calculator takes into account aircraft type, average passenger loads, and fuel burn rates for ascents and descents. So the carbon emissions per passenger can vary widely — sometimes by a factor of two or more from lowest to highest on the same route. And across different routes, it’s not necessarily the same airline that pollutes the least. The type of aircraft and how full the planes are flying can make a particular airline a green leader for one route and among the carbon hogs for another route.

As travelers become more aware of these differences, we hope they will select flights based on which ones transport a passenger point-to-point with the least amount of carbon pollution. The cool thing for consumers is that less carbon means less fuel, which should eventually mean lower ticket prices.

Airline executives take note: TerraPass just gave your customers a tool to help them (and you) fight climate change.

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  1. John - May 19, 2008

    There is a contradiction here since some of the flights pollute more per person because they are not as full. If a passenger took an otherwise empty seat on that flight, the per person output would decrease; whereas, taking a seat on already full flight (with a lower per person emission) would not decrease the per person emission. Therefore, it might be environmentally better to take the flight that you list as the highest output since they have otherwise free seats.
    I think that because of this the calculation should not include the passenger loads.

  2. BCC - May 19, 2008

    I agree with John, for slightly different logic. While looking at *average* emissions per head can be interesting and useful, when making a choice to book a flight, I want one with the lowest *marginal* emissions. I would think that booking on a relatively full flight would be more likely to cause the airline to respond in the future with a bigger plane or more frequent flights on that route, while booking on a relatively empty flight might delay that route getting downsized or cancelled (unless the flight was scheduled as a backhaul to get a plane where it was needed).
    So I would think the best flight, all else equal, would be the one that was pretty, but not really, full.
    Frankly, I fly mostly for business, so price and timing is going to continue to be my main factors for choosing flights. I try to fly as little as possible, and buy offsets as an imperfect solution when I do fly.

  3. Adam Stein - May 19, 2008

    John — you raise a really interesting point. There are actually a number of different ways to apportion responsibility for CO2 emissions. Having heard arguments on both sides, I don’t really think there is a single right way. Thinking in terms of marginal contribution is probably accurate in a lot of situations, but there’s also a compelling argument to be made that flying in less-full planes encourages airlines to maintain wasteful routes.
    Because our data provider TRX has been thinking about these issues quite a bit, I asked them to chime in. Here’s an abbreviated version of the response I got:

    Indeed, this is an interesting issue. I have spoken to many people about this in the past. An argument can be made either way (to use or not use passenger load factors), just as arguments can be made to use or not use cabin seat allocations, or to use or not use cargo adjustments.
    The reasons we chose to include passenger load factors are several. Here are some thoughts off the top of my head. Below I’ve intertwined the concepts of passenger load factors and cabin factors, since they have similar implications for social responsibility.
    1. By using the best estimates for passenger load factors, instead of assuming 100% occupancy, we are closer to determining what is my contribution to CO2 emissions. What is the impact of my choice to fly on one flight vs. another flight? If I have a choice between a fully loaded flight (lower CO2 per passenger per flight) and a sparsely loaded flight (higher CO2 per passenger per flight), and I choose the sparsely loaded flight, I am encouraging the airline to continue flying the sparsely loaded flight, instead of dropping the flight from their schedule.
    2. By using passenger load factors and cabin factors, we highlight the fact that our personal choices have consequences. If I have a first class seat that has 3X the footprint of an economy seat, why should I not be responsible for 3X the CO2 emissions? There is a consideration of social responsibility.
    Another point: the commenter is correct that taking a seat on a sparsely loaded flight would decrease per person emissions. He is wrong in stating that taking a seat on a fuller flight does not decrease emissions. You are still decreasing per person emissions but it is a smaller percentage effect than for the sparsely loaded flight.

  4. John - May 20, 2008

    These are interesting and legitimate points. I grant the point that by being on a flight with a lower load, you might be encouraging the flight to continue when it otherwise might be eliminated (frankly I do not travel enough that I can keep a flight going by merely paying my fare). It all comes back to defining “additionality” that seems to be a consistent issue with calculating emissions and offsets.
    Also, to be clear I was only stating that emissions do not go down per person on a completely full flight; on a 90% full flight the addition seat sold would at least marginally reduce per person emissions. But as BCC noted it also might lead the airline to make a new flight.
    Personally, given the uncertainty, I would prefer a calculator that took out passenger loads (and possibly cargo loads). That way we could see which airlines were using more fuel efficient planes, etc. without the background noise of passenger load.

  5. Adam Stein - May 20, 2008

    Oh, that reminds me — there’s one other thing I should mention here. It really never makes sense to think of these issues in terms of one individual’s actions. Rather, the question should generally be, “What if 1,000 (or 10,000, or more) people behaved in a roughly similar way?”
    Airlines pretty clearly don’t, for example, create a new flight as soon as the last seat on a plane gets taken. Rather, they manage load through pricing: the last seat is expensive, and so people are encouraged to take a less popular flight.
    I’m not really sure how this would swing the analysis. My guess is that if, in aggregate, people gravitated toward full flights and away from emptier flights, you’d see load factors generally increase, which would be a good thing.