Despite a monumental turnout that stretched across every continent, it remains unclear whether the high-profile demonstrations can fundamentally alter the global forces contributing to climate change and compel elected leaders to make the difficult choices necessary to halt the world's warming.
But transformative change is precisely what those behind Friday's marches have demanded - including a swift shift away from fossil fuels toward clean energy, halting deforestation, protecting the world's oceans and embracing more sustainable agriculture.
Friday's far-reaching strikes, which spanned more than 150 countries, come three days before world leaders are set to gather at the United Nations on Monday for a much-anticipated climate summit.
U.N. Secretary General António Guterres has insisted that countries bring with them promises of meaningful action such as vowing to reach net zero emissions by 2050, cutting fossil fuel subsidies and ceasing construction of coal-fired power plants.
The summit will offer a key test of whether the world's nations, which came together to sign the Paris climate accord in 2015, can actually muster the resolve to scale back carbon emissions as rapidly as scientists say is necessary to avoid the worst effects of climate change.
On Friday, the resolve of millions of young people around the world was hardly in doubt.
A growing amount of research suggests that young voters in democracies are increasingly frustrated with political processes, which they feel have failed to address their concerns, most notably climate change.
"I have the feeling that politicians are often just [focusing on] the next vote," said 25-year-old student Jakob Lochner, who was attending the protest in Berlin on Friday. "If you look around, there are so many people on the street; there is kind of a social tipping point."
In Australia, where hundreds of thousands rallied in Melbourne, Sydney and other cities, the impact of inaction on climate change and environmental degradation has made young people lose "faith in our leaders and decision-makers," according to a UNICEF report this year.
Researchers examining the same phenomenon in Europe reached similar conclusions. Almost half of all young European respondents said in a recent survey that they had no trust at all in politics.
That frustration was palpable Friday among the young protesters, who are part of a generation that has become increasingly vocal in their demands that leaders take climate change more seriously - and act more swiftly.
The demonstrations came more than six months after hundreds of thousands of students staged a similar coordinated effort to demand urgent action on climate change, and the latest iteration was just as fervent.
In London, tens of thousands marched past 10 Downing Street and the Houses of Parliament, some holding aloft signs that read "Winter is NOT coming" and "I'm taking time out of my lessons to teach you."
"We're doing our bit, eating less meat, using less plastic," said Lickman, the 13-year-old demonstrator. "But it's still on the government to do something."
Protesters in climate-conscious Germany held more than 500 events to mark the global climate strike on Friday, including a large demonstration at Berlin's Brandenburg Gate.
The demonstrations in Germany come as Chancellor Angela Merkel's government faces increasing public pressure to take bold climate action following heat waves and protests dubbed Fridays for Future throughout the country.
As the demonstration swelled, drawing citizens of all ages, Merkel announced a wide-ranging package aimed at getting Germany back on track to meet its climate targets.
Berlin has pledged to cut its emissions by 55 percent from 1990 levels by 2030. The package includes more than $60 billion in investment in areas such as trains, electric vehicles and subsidies for green buildings, according to German media.
In Moscow, Arshak Makichyan, a 24-year-old violinist, staged a one-man protest after the government rejected his application to hold a group demonstration, the BBC reported. "I thought climate change was just science, but Greta had the right words to explain why it should worry all of us," he said. Russia, which has been hit hard by climate change, ranks as the world's fourth-largest emitter of greenhouse gases after China, the United States and India.
In Brussels, the young and not-so-young protested with signs in English, French and Dutch.
"I am here because we want adults to act," said Caroline Muller, 13, who has protested in the past. "It is time to do something."
Among the largest, most high-profile protests Friday was the one in New York, led by 16-year-old Swedish climate activist Greta Thunberg, who has inspired the protest movement with her solitary school strikes outside her country's parliament beginning last summer.
Even before the strike in Manhattan officially began Friday, Foley Square teemed with colorful signs and shouting teenagers, and the swelling crowd spilled into the surrounding streets.
"Climate change is not a lie, we won't let our planet die," the masses chanted.
"Our planet is not for profit!"
Organizer Alexandria Villasenor, the 14-year-old who helped spark New York's climate strikes when she began protesting in front of the United Nations 10 months ago, smiled as she took in the teeming crowd.
"The strike today is going to change the conversation [at next week's U.N. climate summit]," she said. "They have to listen to us now."
Ultimately, organizers estimated that more than a quarter-million protesters crammed into Lower Manhattan. In Battery Park, a sweaty throng waited beneath the fierce midday sun in front of a stage where Thunberg would later speak.
The speeches from teenagers were fiercely critical of those in power, both in government and in the corporate world.
"Their complacency is killing me," said Isabella Fallahi, a young organizer from Indianapolis, who said Democrats and Republicans are equally culpable for the lack of climate action. "Both parties are guilty of silence. Politicians don't simply get a medal for believing in facts."
Kevin Patel, a fellow youth organizer from Los Angeles, leaned toward the microphone: "You are either with us in this fight or you are against us."
Thomas Jimenez, 16, Lola Allen, 15, and Crystal Lantigua, 16, juniors at Fort Hamilton High School, had raced to secure a place in front of the stage.
"Adults have a lot of opinions about our generation," Jimenez said. "But I think we're strong and powerful. It blows my mind to see kids our age make such a big difference."
Behind him, a sea of handcrafted signs hinted at the sense of anger and frustration among his peers.
"You know it's time for change when the children act like leaders and the leaders act like children," read one.
"I'll take my exams if you take action," read another.
"Policymakers don't get it," said Yujin Kim, a 17-year-old South Korean student who had traveled to New York for a U.N. youth summit. "They're not going to be here in 30 years. And we are. We're going to keep speaking out until they listen."
Organizers said more than 1,100 strikes took place across all 50 states on Friday. The strikes were planned largely by teenagers, in between soccer practices and studying for math exams, but a growing number of adults also have begun to offer their support.
New York and Boston public schools granted students permission to skip school for the strikes. For students in other districts, more than 600 physicians signed a "doctor's note" that reads, "Their absence is necessary because of the climate crisis."
Numerous companies, including Ben & Jerry's, Patagonia and the cosmetic company Lush, closed their doors Friday in solidarity with the youth and encouraged employees to attend the Friday's strike.
Back in Washington, 35-year-old Allyson Brown pulled her 5-year-old daughter out of school and headed toward the Mall, where she planned to impart a lesson on how to push for change.
"This," she said, "is education for today."
