Some four million people filled city streets around the world, organisers said, in what was billed as the biggest ever protest against the threat posed to the planet by rising temperatures. Thunberg began skipping school on Fridays in protest outside her country's Parliament, demanding immediate action in response to the climate crisis.
But on Friday, she was joined by a crowd of more than 60,000 people, marching through the streets of NY.
It's very fun to travel to different countries and see how the debate is going there and how much people seem to be aware, and how climate activists work, because they work so different in different parts of the world.
Other activists said they were prepared to take strong personal action, such as pledging not to have children until their governments acted on climate change.
In Berlin, more than 100,000 people were estimated to be in attendance at strike events while in New York City, the Department of Education allowed 1.1. million students to skip school to participate in the strikes-with parent permission, of course. In December, Thunberg's speech at a United Nations climate conference, in which she accused world leaders of "stealing their [children's] future in front of their very eyes", made headlines around the world.
Other participants spoke about efforts they are leading to cut emissions or reduce climate impacts back home.
Thunberg has been an influential leader in the youth climate change movement.
"Can you really look them in the eye and say, 'No, sorry, I couldn't do anything because that country over there didn't do anything, so if they're not going to do it then I'm not.' That is shameful and that is cowardly", Margolin said. As tens of thousands came out in various cities of Australia, Germany and U.S. it proved to be a wake up call for rich countries and the United Nations to find ways to tackle impact of global warming.
The protests also highlighted resistance from climate change skeptics.
"I have granddaughters. I want my granddaughters to live in a liveable planet".
Solomon Yeo, 24, a law student from the Solomon Islands, said he and others were working to fill gaps in worldwide law, in part by drawing links between a warming climate and how it threatens human rights.
"The climate and ecological crisis is the political crisis of our time".
"We wanted to avoid inciting terms such as "strike" and 'demonstration", said Saori Iwano, a 16-year-old FFFT member.
"The two can't be delinked and I think new petrochemical plants too close to residences in a diversifying economy does not fit with that vision", she said.
The Climate Strike is the first time students have been so widely encouraged to voice their opinions on the public stage.
But Guterres struck a more optimistic note on Saturday, telling youth leaders that "there is a change in momentum" on the issue of climate change.
NY protester Pearl Seidman, 13, hoped the demonstration would tell the Trump administration "that if they can't be adults, we're going to be adults".
"It's one that you'll be hearing more about both from Microsoft and our peers in the broader tech sector as this moves forward".
He said the region's experiencing a severe drought, and the city ran out of water a few months ago; they're having to bring water in by train. "Keep your mobilization and more and more to hold my generation accountable", Guterres said.
This movement we are planning on continuing.