KATOWICE - What could have been a two-hour journey by plane turned into a two-day road trip for a Swedish teen and her father - all for the sake of the environment.

Instead of flying from Stockholm to Katowice, Poland, to take part in the ongoing United Nations (UN) climate change talks, 15-year-old Greta Thunberg and her actor father Svante, 49, drove the 1,600km in an electric car.

Speaking to The Straits Times on the sidelines of a climate protest in the Polish city on Saturday (Dec 8), Greta said: "There is a lot you can do as an individual to take climate action. First, you can make changes in your everyday life, by not flying, going vegan, and not buying new things.

"You can also learn more about the climate crisis, try to understand it, realise what it actually means, and to spread the word to other people, talk about it with them, and put pressure on people in power."

Greta is not just dishing out advice - she also practises what she preaches.

Earlier this year, she made global headlines when she refused to go to school in order to pressure the Swedish government to take more drastic climate action.

She is still on this climate strike - but instead of skipping classes five days a week as she did in August, she now misses classes only on Friday to sit on the steps of the Swedish parliament.

Mr Thunberg, Greta's father, told ST: "We were anxious before she got started with the climate strike, because when you do something like that, you expose yourself to huge risk.

"People don't understand the risks of climate change, and they might think her strange. So we told her that if she wants to do it, she would have to do it by herself, that she would have to have all the answers and facts, and double and triple check whatever she says."

It turned out that despite her diminutive appearance and shy demeanour, Greta had an iron will. She stuck to her guns, and the teen has since emerged as the face of the youth movement for climate action. In Katowice for COP24, she has given interviews and taken part in panel discussions. But she has her doubts about the success of these international negotiations.

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Said Greta: "We have done this (organised conference) before and nothing comes out of it. We need to start treating a crisis as a crisis, because if we don't, then nothing is going to change." A tipping point is needed, Greta said, and that is where citizen action comes in. "Young people have always been underrated," she said, but age is just a number.

Greta has inspired many others to take greater climate action, and her example has demonstrated the ripple effect that can spread from one person's action. Scores of students around the world, from Canada to Australia, have also gone on climate strike to call on world leaders to clean up the environment for the next generation.

Greta's parents, too, have been gradually influenced over the past five years by their green-minded child. The Thunbergs, including her 13-year-old sister Beata, now adopt an environmentally-friendly lifestyle.

They switched to a vegan diet, and Greta's parents also invested in an electric car about three years ago. They avoid buying new things as much as possible, or opt to buy second-hand, said Mr Thunberg. Greta's mother Malena Ernma, an opera singer, has also given up her international career in order to reduce her carbon emissions, according to the Guardian.

Mr Thunberg said: "Greta gave us articles, and we read more about climate change, and I was shocked that I didn't know. I was shocked by my own ignorance, and society's ignorance, about climate change."

Adults today have failed her and those in her generation, said Greta. She added: "We need to make our voices heard, and say this is enough. This is the biggest crisis that humanity has ever faced, and we have to do something about it now, because tomorrow it might be too late."