GRETA THUNBERG is currently afloat somewhere on the Atlantic Ocean. The 16-year-old Swedish climate-change activist is sailing from Britain to New York, where she will attend the UN’s Climate Action Summit. With cramped quarters, no toilet and the potential for rough seas, the two-week voyage will be uncomfortable. Ms Thunberg has described the experience as “camping on a rollercoaster”. By air, the journey would take just eight hours. But because of the greenhouse-gas emissions associated with air travel, she refuses to fly.

Ms Thunberg is not the only one. In the past 18 months the share of Swedes who say they travel by rail instead of air when possible has nearly doubled, from 20% to 37%, according to SJ, Sweden’s largest train operator. In 2018 SJ sold 1.5m, or 5%, more tickets than the previous year. Meanwhile, the number of passengers travelling on domestic flights in the country fell by 8% from January to April this year, according to Swedavia, which operates Sweden’s 10 busiest airports (there was a more modest decline of 2.8% for international flights). This compares with a 4.1% year-on-year rise in overall European air-passenger traffic in the first five months of 2019.

Sweden, a nation of frequent flyers, has grown increasingly ashamed of its globe-trotting in recent years. The country has even coined a word for the phenomenon. Flygskam, or “flight shame”, describes the embarrassment that Swedish travellers feel about their environmental impact. The phrase was the rallying cry of an anti-flying movement championed by Björn Ferry, an Olympic biathlete, who stopped flying in 2015. In 2017 he was joined in his boycott by 10 Swedish celebrities. Last summer, amid a heatwave and raging wildfires, more Swedes turned away from air travel. “Flygfritt 2019” (No-fly 2019), a social-media campaign, saw 14,500 people pledge not to fly this year. Organisers aim to boost this figure to 100,000 in 2020.

Other possible explanations for the decline in Swedish air travel include a slowing economy, a new tax on flights introduced last year and the bankruptcy in 2018 of NextJet, a Swedish regional airline. But Rickard Gustafson, the boss of SAS, a Scandinavian carrier, told a Norwegian newspaper this year that he was “convinced” that flygskam was responsible for the recent decline.

Flygskam has travelled beyond Sweden, becoming flugscham in German, lentohapea in Finnish and vliegschaamte in Dutch. It has also inspired a spinoff Swedish expression: tågskryt, or “train brag”, for when someone shows off about their virtuous, rail-based holidays.