Greta Thunberg found a last-minute ride back across the Atlantic thanks to a pair of YouTubers after a crucial UN climate-change summit got moved from Chile to Spain

• Greta Thunberg is setting sail back across the Atlantic with an impromptu motley crew: two YouTuber Australians, their 11-month-old son, and a professional sailor.
• The Australian couple answered Thunberg's call for help getting back to Europe after the year's most important UN climate-change summit, COP25, was moved from Chile to Spain.
• It will take about three weeks to sail to Spain in the couple's 48-foot catamaran called "La Vagabonde." Thunberg should arrive just in time for COP25.
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Greta Thunberg is hitching an impromptu boat ride back to Europe.

The 16-year-old Swedish climate activist refuses to fly, because airplane travel has such a heavy carbon footprint - a single round-trip flight between New York and California generates roughly 20% of the greenhouse gases your car emits in a year. In Europe, this means she typically travels by train. 

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This summer, Thunberg sailed from Europe to New York in a zero-emissions sailboat. Upon arrival, she addressed international leaders with a powerful speech at the UN Climate Action Summit in New York. Since then, she's been traveling across North America with plans to make her way to Chile to attend this year's most important climate summit, the UN COP25.

But Thunberg's unconventional travel methods posed a dilemma when the summit was moved to Madrid, as the Chilean capital, Santiago, erupted in riots and protests. The move left Thunberg stranded on the wrong side of the ocean.

On Tuesday, the activist said she'd found a last-minute ride with an Australian couple, their 11-month-old son, and a professional sailor.

"So happy to say I'll hopefully make it to COP25 in Madrid," Thunberg tweeted with a photo of the motley crew. "We sail for Europe tomorrow morning!"

The trip will take about three weeks, according to The New York Times. If all goes as planned, Thunberg will arrive just in time for COP25, which starts December 2.

Even with the time crunch, Thunberg did not want to take an airplane.

"I decided to sail to highlight the fact that you can't live sustainably in today's society," Thunberg told The New York Times on Tuesday. "You have to go to the extreme."

When Thunberg put out a call for help getting back to Europe, Riley Whitelum responded on Twitter.

"If you get in contact with me I'm sure we could organise something," he said on November 4.

Whitelum and his wife, Elayna Carausu, have been sailing the world and making YouTube videos of their adventures since 2014. 

Within a week, the Times reported, they had arranged Thunberg's voyage in their 48-foot catamaran, "La Vagabonde."

Nikki Henderson, a professional sailor from Britain, will join the team. The couple's son, Lenny, and Thunberg's father, Svante, will also be along for the ride.