The ?????? ????? ??????global fight against climate change has seen serious momentum of late, thanks in part to Greta Thunberg — inspiring millions to march against government inaction around the world is no mean feat. But there's a particular movement that the Swedish teen activist has also helped to popularise.

It's called 'flygskam.'

'Flygskam' is Swedish for 'flight shame' and it's growing into a pretty formidable strategy. Thunberg wielded it when, instead of taking a flight from the UK to New York, she sailed across the Atlantic aboard a zero-emissions racing yachtthis August. Her two-week expedition shed light on the immense impact commercial aviation has on climate change.

In 2018 alone, international air travel was responsible for 2.4 percent of global fossil carbon dioxide (CO2) emissions. While it may seem like an insignificant number, if commercial aviation were treated as a country it would be the sixth biggest fossil CO2 emitter in the world. To make matters more pressing, the growth of commercial aviation is exceeding expectations and with that, emissions attributed to it are on the up.

Greta Thunberg aboard Malizia II Credit: Kirsty Wigglesworth - WPA Pool/Getty Images

But where exactly does the term 'flygskam' come from? According to Ola Karlsson, a language advisor at the Swedish Language Council, 'flygskam' is a compound of 'flyg', which means flight, and 'skam' — shame. Together, the term embodies a feeling of guilt over taking flights.

"It's the feeling you have that your habit of flying is a morally reprehensible act from an environmental point of view," he told Mashable.

And so far, it's working. BBC reports that according to a WWF survey, 23 percent of the Swedish population says it has altered its flying behavior since 'flygskam' entered the country's vocabulary. And although it's hard to directly associate that shift with the term itself, a new survey by Swiss bank UBS suggests that flying shame is indeed leading people to fly less, not just in Sweden but in the UK and the U.S. as well.

"New words like flygskam can convey some kind of message and indirectly influence our opinions," Karlsson said. "At least in Sweden, train traveling has increased distinctly over the past year or so and flying has decreased."

In Sweden, the number of passengers embarking on domestic flights decreased by three percent in 2018. In the same year, SJ, a state-owned train operator, told Mashable in a statement that it carried two million more passengers than the year before — a six percent increase. The 2019 trends are also in favor of rail transport, with SJ reporting that it's seen customer numbers rising between 8-9 percent in the first half of the year.

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How to avoid guilt trips

Woman Looking Through Window While Traveling In Airplane Credit: Getty Images / EyeEm Premium

'Flygskam' seems to have had an impact in Sweden, but is instilling this sense of shame around the world the right thing to do? After all, only a small percentage of the population is privileged enough to consider frequent flying a choice.

"A disproportionate amount of the flying is done by a relatively small group," Dan Rutherford, the aviation program director at the International Council on Clean Transportation, told Mashable.

"In countries like the UK and the United States, typically, about 15 percent of the population takes about 70 percent of the flights," he said. "So if you're in that group, then probably you should be thinking about changing your behavior."

In simple terms, if you take more than five flights per year, cut it down. And even if you rarely board a plane, there are still things you can do to fly more efficiently. Or as Rutherford calls it, "fly like a NERD," an acronym that stands for new, economy, regular, and direct. In essence, it means we should be trying to take direct flights in economy class, executed by regular-sized, newer airplanes.

Original image has been replaced. Credit: Mashable

But wait, can't you just offset your carbon emissions when booking your flight, by ticking that little box and donating to carbon reduction projects? It's a controversial topic, and is probably better than doing nothing. And sure, it might make you feel less guilty for flying, but according to Professor Susanne Becken, a professor of sustainable tourism at Griffith Institute for Tourism, "a carbon offset helps to mitigate climate [change] elsewhere, but it does not negate emissions."

There are other options out there, Becken said, with a more immediate effect. These are what she calls 'insetting', in which you assume that you have a certain carbon budget which you are not supposed to exceed.

"If I take a flight, it will probably destroy my budget and I will have to try even harder in some of the areas, like swap my car for public transport or make sure my next trip is by rail," she said. "In that sense, offsetting becomes "insetting" where I can invest resources (time and money) into activities that actually truly reduce carbon."

Young adult polar bear sitting on flakes of sea ice at Svalbard Credit: Getty Images

The NERD acronym, offsetting, and insetting are all good enough options to consider when you cannot actually make an informed decision about the most efficient flight that you could book. As Rutherford explains, airlines "control basically every lever you need to reduce the carbon intensity of flying. [...] So it's really important that airlines and then governments move in the direction of better data disclosure."

In Sweden, changes in transparency are already being considered. "There's been a proposal for airlines to disclose the carbon intensity of their flights within Sweden," Rutherford said. "So that's a good example of a government that's taking positive steps in this direction."

It might not be too long before flight search engines are able to display flights with carbon labeling, which would make it easier for people to make informed choices when it comes to flying in the most fuel-efficient way possible.

Until then, it might be up to the power of 'flygskam' to get us flying like NERDs.