When Greta Thunberg stepped on to the platform at Stockholm Central station on Thursday after completing her European tour to raise awareness of climate change, an unassuming 69-year-old who runs a tiny travel firm was there to greet her.

Ivar Karlsson has found his business in the spotlight as appetite grows for alternatives to flying. It was Karlsson, whose company specialises in rail-only holidays, that Greta and her father contacted to book their trip, which took in stops in Strasbourg, Rome, London before heading back to Sweden.

Why I only take one holiday flight a year Read more

The success of Sweden’s “flygskam”, or “flight-shame”, movement means that Karlsson struggles to respond to calls or emails from less high-profile customers than Greta. He said he had been working 16-hour days, nearly seven days a week, trying to meet the surge in demand, with bookings at his Centralens Resebutik agency increasing eightfold this January compared with two years ago.

“We were already stretched to a limit last year and now we’ve doubled that,” said Karlsson, who is based in the city of Kalmar. “If we had greater resources, then we could have done much more. The demand and interest is much, much bigger than we can cope with.”

Karlsson, his co-owner Maria Petersson, and their six permanent staff, have been unable to answer the volume of calls and emails coming in, leading to much grumbling on the Tågsemester (train holidays) Facebook group.

“There are some limits with our capacity, as we are only human beings,” he said. “There are at least 30 people calling all the time at the same time. The telephone is constantly busy and then the whole thing breaks down.”

Climate change is particularly visible in Sweden, with the Swedish Meteorological Institute reporting at the start of this month that the average annual temperature was rising twice as fast in the country as the global average. The country last year experienced the hottest and in many parts the driest, summer since records began, along with some of its worst ever forest fires.

Play Video 2:04 The Greta Thunberg effect: her activism in London in two minutes - video

With train travel generating 15g of CO 2 per kilometre compared with about 100g for flying, environmentally conscious Swedes such as Greta are stopping flying, or at least reducing the number of flights they take. The World Wildlife Foundation released a survey indicating that nearly one in five people in Sweden had opted to travel by train rather than plane for environmental reasons.

The Tågsemester Facebook group has gained 80,000 followers since it was launched in 2014, pushing its founders to start a rail-only travel agency, launch a pledge campaign for a flight-free 2019, and host a conference.

Ving, a Swedish travel agency owned by Thomas Cook, has jumped on the bandwagon, launching a £1,500-a-head charter train package deal from Stockholm to Davos in Switzerland.

On Karlsson’s advice, Greta and her father, Svante Thunberg, took advantage of a February offer from InterRail allowing them to travel first class for the price of a standard ticket on their long journey.

“She used that offer to buy a very extensive InterRail ticket, meaning she can travel in a rather peaceful environment, which I think was necessary as she has to write her speeches,” Karlsson said.

Facebook Twitter Pinterest Greta talks to journalists as she arrives in Zurich, Switzerland for the World Economic Forum Photograph: Adrian Reusser/AP

“She managed the whole trip, and I don’t think the train was the toughest part of it, because what she has experienced in the past week has been more than humanly possible.”

According to the carbon dioxide calculator on the Loco2 train booking site, Greta and her father each saved about 400kg of CO 2 by not flying: about a tenth of the average Swede’s total annual carbon emissions.

But while Greta may be a standard-bearer for the no-fly movement internationally, Karlsson said another of his customers, the television ski commentator Bjorn Ferry, had done most to get the movement rolling.

Ferry announced last year that he would only cover events he could travel to by rail. Swedish television then broadcast a five-episode TV documentary about his efforts to persuade others in his hometown in Lapland to do likewise.

Karlsson, who ran part of the international division of SJ, Sweden’s national rail company, in the 1980s and 1990s, likened the current surge to the years after the fall of the Berlin wall, when Swedes rushed to buy rail tickets to eastern Europe.

But unlike then he said he thought the current trend would last. “I believe that once people have made this shift, saying: ‘Well, no more air travel for me, now I will stay on the ground,’ they will stick with it,” he said.

“That’s my rather solid conviction, because I’ve spoken to so many people, and it’s rather seriously based. I believe it will be something rather stable.”