Since then the Swedish teen activist has marched with the Fridays for Future demonstrators in New York City, testified before the US Congress and met former US President Barack Obama in Washington, DC.
On Friday, the fearless young Scandinavian warrior shepherded tens of thousands of students striking from school in New York with a loud refrain not just for their teachers, but for world leaders gathering at the UN Climate Action Summit next week.
“Fossil fuel CEOs will stop at nothing to squeeze every last drop of money from the earth,” said Varshini Prakash, executive director of the Sunrise Movement, the US youth-led coalition calling for action on climate change. “[We] will strike again and again until we win.”
Billed as the largest climate action in history, the New York marchers followed some 4,500 global rallies that began hours before in cities such as Kiribati, Sydney, New Delhi, Islamabad, Nairobi and London. Early unofficial estimates put the global total at more than three million participants.
“It’s amazing,” Prakash told Al Jazeera of Friday’s attendance. “This tremendous amount exceeded expectations. I woke up this morning to see my Twitter feed flooded with images [from] around the world.”
She said “a new movement is emerging as political institutions fail”, adding that leaders needed to “wake up and grow up, and take this seriously”.
“The momentum from today shows that any candidate for the American presidency who wants to win our generation’s votes must commit to making the Green New Deal the number-one priority of their administration,” she added.
Friday’s strikes come after a new poll this week showed that one in four US teenagers has taken climate action. The Washington Post-Kaiser Family Foundation poll also found that a majority of US teens are afraid of the effects of climate change.
Nine-year-old Pilar Medel from the Bronx borough of New York City, came to the strike with her mother after attending some classes in the morning.
“I come because Greta is a girl just like me, and I want to help her make this planet live,” she told Al Jazeera, unfurling a large blue banner with a large photo of the Earth from space.
“I want to do something for the world,” said Ralph Davis, 13, a student also from the Bronx who has attended climate rallies before. “But there are a lot of things that need to happen and some of it is not possible.”
Student Archibald Richie yelled, “Dinos thought they had time, too, but they died.”
The 15-year-old from Manhattan added that “we have the time to make a difference.”
Youth around the world have been protesting for more than a year, but on Friday adults were formally invited – perhaps an indication young people are earnestly pressing on with demands in the political arena.
They seek an end to fossil fuels, justice for front line communities and 100 percent renewable energy.
“We’re residents of planet Earth,” said Karen Naftali, 39, who attended the rally in Lower Manhattan at Foley Square. It’s important to show support [for the youth]. They’ll be here for longer, we’re old.”
New York City’s school system gave students permission to leave class to strike, a sign that government officials realise too the role that the next generation is playing in the climate fight.
Jumaane Williams, New York City’s public advocate, also joined the young protesters.
“I’m ecstatic,” Williams said of the number of students who skipped school to attend, adding that he had written letters to administrators successfully petitioning to have amnesty for striking students.
“I hope they’ll ignore the orange man in the White House on all things climate change,” Williams told Al Jazeera, referring to leaders convening at the UN who have scolded US President Donald Trump for deciding to pull out of the Paris Agreement.
“Give us a couple years [for a change in national leadership]. Hopefully about two.”
Meanwhile, around 1,000 Amazon employees joined the strikes on Friday over their company’s climate inaction. Patagonia and Ben & Jerry’s were among the companies that announced their stores will temporarily close on Friday in solidarity with marchers.
Some 6,000 websites – including Kickstarter, Tumblr and WordPress – went dark Friday to indicate that they are also on the same page.
Protests in the US popped up from Chicago to Pine Ridge, South Dakota. The events also marked the second anniversary of Hurricane Maria’s devastating effects on Puerto Rico.
The rallies kick off Climate Week NYC, with escalated actions planned across the city and country as the UN General Assembly gets under way with a youth climate forum on Saturday and Climate Action Summit on Monday.
“I had no idea how big it would be today,” said Azalea Danes, 16, one of the leaders in Fridays for Future who has pledged to hold polluters accountable.
Danes described the crowd as “huge, massive”, telling Al Jazeera that “elected officials have to take action, and if they’re not with us, they’re underneath us.”