NYKOPING, Sweden — School's out for summer and Swedish lawyer Pia Bjorstrand, her husband and their two sons are shouldering backpacks, ready to board the first of many trains on a whistle-stop vacation around northern Europe.
The family is part of a small but growing movement in Europe and North America that's shunning air travel because it produces high levels of greenhouse gas emissions. While experts say fighting climate change will require bigger and bolder actions by governments around the world, some people are doing what they can to help, including changing long-held travel habits.
The trend is most prominent in Sweden, where the likes of teen climate activist Greta Thunberg have challenged travelers to confront the huge carbon cost of flying.
"Even I, who was climate aware 10 years ago, didn't think about flying in the way that I think now," said Bjorstrand as she waits on the platform of Nykoping station in eastern Sweden. "I didn't know that the effect of flying was so big. So we flew everywhere."
Airlines argue that flying accounts for just 2% of man-made greenhouse gas emissions and increasingly efficient planes now use about the same amount of fuel per passenger as a half-full car. Yet the ease and falling cost of air travel is enabling more people to fly more often, meaning airline emissions are soaring even as other sources decline.
In 2013, commercial carriers emitted 710 million tons of carbon dioxide. This year, industry group IATA predicts airlines' emissions of CO2 will reach 927 million tons, more than an industrial country like Germany. The figures don't include other factors that scientists say increase the greenhouse effect from flying.
Planes fare particularly poorly compared with rail travel, especially in countries where trains can draw on a plentiful supply of renewable energy, like Sweden.
Bjorstrand's train journey from Nykoping to the Danish capital Copenhagen weighs in at 5.3 pounds of CO2 per person, according to an online calculator created by the Germany-based Institute for Energy and Environmental Studies consultancy. That compares with over 260 pounds of CO2 for a one-way flight.
Such amounts quickly take a big chunk out of the annual carbon budget of 2,000 kilograms per person that scientists say would be sustainable.
The rail journey is almost twice as long by train - 5 1/2 hours compared with three hours of flying and transit - but that's fine with the family. There'll be plenty of time for Oscar, 9, to pore over his comic books and Gabriel, 11, to read up on World War II history or just watch the lush green forests and lakes of southern Sweden glide by.
Pushback against flight-shaming is coming from some unlikely sources.
Anders Levermann, a scientist at the Potsdam Institute for Climate Impact Research, believes that the world needs to stop adding carbon to the atmosphere by mid-century if it wants to keep average temperature increases below 3.6 Fahrenheit as outlined in the 2015 Paris accord. But he said the climate movement shouldn't focus only on air travel.
"At the moment it is treated like whales for biodiversity," Levermann said. "It's a poster child."
A more effective way to reduce emissions would be to pressure political leaders into taking decisions that have a nationwide or global effect, rather than guilt-tripping individuals into minimizing their carbon footprint, said Levermann.