It is a very interesting time to be working on aviation and climate. Climate activists in Europe, organizing under the umbrella of flygskam (Swedish for “flying shame”) and Fridays for the Future, are questioning whether the social benefits of air travel are outweighed by its environmental costs. Some have begun to forego air travel or opt for other modes of transport. And airlines and governments are beginning to take notice, with Dutch carrier KLM going so far as to suggest that, in certain cases, travelers shouldn’t fly at all.

Clearly, much of the airline industry doesn’t agree. Earlier this year, IATA’s Director General and CEO, Alexandre de Juniac, demanded that reporters “stop calling us polluters” and claimed that arguments linking flying to climate change are based upon “fake news.” Even more extreme are aspiring supersonic manufacturers like Boom, whose CEO argues that speed is a “moral imperative” and who’s company recently claimed that increases in subsonic air traffic highlights the need for even faster supersonic designs. Those aircraft, mind you, could be 5 to 7 times as carbon intensive as comparable subsonic designs.

Our recent 2018 commercial aviation CO 2 inventory identified the U.S. as being responsible for about one-quarter of both passenger traffic and the associated carbon dioxide. So, should you be ashamed to fly if you’re an American who is concerned about climate change?

Let’s look at the numbers. We estimate that global civil aviation accounted for 918 million tonnes (Mt) of CO 2 in 2018, or about the combined emissions of fossil fuel use in Germany and the Netherlands. Of that, passenger flights within and departing U.S. airports were responsible for 182 Mt of CO 2 . World Bank data shows that tourism flows in and out of the U.S. are roughly symmetrical. Thus, it’s reasonable to apportion that CO 2 to U.S. residents. So, the average U.S. citizen emitted about 550 kg of CO 2 last year due to passenger aviation, or about 3.3% of all fossil fuel CO 2 from the U.S. last year.

To determine if the average American should be ashamed to fly, you must determine what constitutes “average”. The results of a 2017 IPSOS survey of American travelers, summarized in the graphic below, backs up the contention that, for the average American, flying actually isn’t actually a big part of their carbon footprint.

As shown in the graphic, American adults can be divided up into three groups. About one-half (53%) of those didn’t fly in 2017. Another one-third (35%) flew 1 to 5 times per year and are responsible for about one-third of all flights. The remaining minority of Americans –12% to be exact – who fly six or more times per year were responsible for about two-thirds of all flights in 2018. That’s an average of 14 flights per person.

How does that translate to CO 2 emissions? The IPSOS study doesn’t break down exactly which trips – domestic vs. international, economy vs. business class – these frequent fliers take. But we can get a ballpark sense of how these trips translate to emissions by randomly assigning trips to individuals in proportion to how often they fly. (This approach likely undercounts the carbon footprint of frequent fliers, who are more likely to fly carbon-intensive business class, so we’re erring on the side of being conservative.) The table below breaks down U.S. aviation CO 2 emissions by trip frequency.

Group Trips per year (2017) Percent of American adults Percent of all trips Aviation CO 2 per person Non-fliers 0 53% 0% 0 tonnes Occasional fliers 1 or 2 21% 13% 0.33 tonnes Infrequent fliers 3 to 5 14% 19% 0.83 tonnes Frequent fliers 6+ 12% 68% 3.1 tonnes

So, the answer to “should Americans concerned about climate change be ashamed of flying?” is an equivocal “probably not*”. Not because per capita emissions aren’t significant, but rather because the average American doesn’t fly that often. If you randomly choose an American and calculate their aviation carbon footprint, more often than not it would be zero. If you choose someone who flies 5 or fewer times per year, their aviation carbon footprint would only be about 3% of the 16 tonnes of fossil CO 2 the average American releases in a year.

However, the asterisk, or disclaimer, is needed because if you choose an American adult who is a frequent flier, you get a very different picture. Three tonnes of CO 2 per person is substantial, particularly by global standards. If all Americans were frequent fliers, U.S. aviation jet fuel use would increase about sixfold and planes would easily surpass passenger cars as the largest transport source of CO 2 in this country. If everyone in the world flew like American frequent fliers, global oil consumption would increase by 150% and CO 2 emissions from fossil fuel use by more than 60%. This would make it impossible to meet international goals to avoid the worst impacts on climate change.

So, although aviation dominates the carbon footprint of a relatively small number of frequent fliers, it's wrong to conclude that trying to convince travelers to reduce a “minuscule” amount of CO 2 isn’t worthwhile. Our global climate literally cannot tolerate widespread frequent flying, and people who currently fall into that group probably do need to modify their behavior.

If you are an American that flies a couple of times per year, you probably shouldn’t worry too much about boarding a plane. Instead, focus your efforts on finding fuel-efficient carriers, which can make a big dent in your carbon emissions. If you are a frequent flier who cares about climate change, then you should think more carefully about how many of those trips are truly necessary, particularly if you travel in more carbon intensive business class.

I fly only once or twice each year for leisure, but much more for work. Last year, I flew 100,000 km in economy to help set environmental standards for ships and planes at the UN level. I’ve developed a variety of tricks to reduce the climate impact of flying when I absolutely need to. Next time around, I’ll unpack how you can manage your carbon footprint by flying like a NERD. Until then, by all means, peruse our library of research on what governments and industry can do to start decarbonizing the aviation industry.