BERLIN — Tens of thousands of teenagers across Europe skipped school again Friday. They’ve been congregating weekly in streets, plazas and parks, but not for a concert or weekend adventure. They’ve gathered to show the grown-ups that they will no longer play by their rules, and to demand that adults protect their future from climate-change disasters.

These teens are part of a movement that has spread across the European Union and is expanding globally. Thousands of Britons took part in this week’s protests, include those who took to the streets in London holding aloft placards that read “The ocean is rising and so are we” and “Act now or swim later.” A group gathered outside 10 Downing Street, the residence of the British prime minister, and chanted: “What do we want? Climate justice. When do we want it? Now.”

In late January, some 30,000 students protested in three Belgian cities. The same week, more than 10,000 skipped school in Germany, holding signs that read “Make our planet great again” and “There is no Planet B.”

The list of countries in which teens are protesting is growing, and they are organizing what is being billed as a global strike on March 15 that will most certainly include protests in Germany, Belgium, Switzerland, the Netherlands, France, Britain, Australia and the United States. 

“We don’t have time anymore,” said 14-year-old Jolante Vogel, who came from Jena, a city in eastern Germany, to attend the “Fridays for Future” protest in January.

“We have to act now,” she said. “I’m worried that one day we can’t live on this planet anymore, that there will be vast poverty and storms and that we won’t be able to do anything to reverse the trend.”

This was Vogel’s fourth time skipping school to attend a Friday protest, and she said that although her teachers understand her reasons, they want her in school. As a sort of compromise, she and her classmates sometimes protest at school and sit in the schoolyard to study. 

“We don’t miss school because we’re lazy or because we don’t want to go to school,” said 18-year-old Jakob Blasel, a high school senior from the northern city of Kiel who helped organize the January protest in Berlin. “We can’t go to school, because we have to strike. We have to deliver an uncomfortable message to our leaders that it can’t go on this way.”

The teens are following the lead of 16-year-old Swedish activist Greta Thunberg, who in August started skipping school on Fridays as an act of protest. Thunberg in December delivered a defiant speech at a global climate-change conference in Poland: “You say you love your children above all else — and yet you are stealing their future in front of their very eyes,” she said to a room full of policymakers whose climate negotiations have been largely stuck in political gridlock. “Until you start focusing on what needs to be done rather than what is politically possible, there is no hope,” she added. “We cannot solve a crisis without treating it as a crisis.”

Young protesters across the globe have echoed and amplified that message on social media platforms and in the streets.

Rosie Fowkes, 17, said that social media helped mobilize the protesters for Friday’s demonstration in London. She came to show the government that “young people care and young people are worried” about the future of the planet, she said.

“People often accuse our generation of being on social media too much and focusing on really unimportant stuff,” Fowkes said, “but I think it’s really cool that we all can gather and show ourselves, and show older generations, that we can use these powers for good and take matters into our own hands.”

Her friend Ella Summers, 17, said the issue is urgent. “We have so much going on in the world that we need to take care of before we take care of our next exam,” she said.

The youths’ climate protests are growing, rivaling in size some of the more noted protests in Europe, such as the “Yellow Vest” protests in France, which in their 13th week continued to draw tens of thousands of people, though in diminishing numbers

“This is the first movement that really addresses the older generations for being responsible,” said Mathias Albert, a youth researcher and political-science professor at the University of Bielefeld. “What these young people see is that it is obviously difficult for parts of the older generation — especially those who have specific economic interests — to change their ways.”

Despite Germany’s image as a global environmental leader, the country is far from meeting its climate goals. It’s transportation emissions have gone up over the past three decades. At this rate, it is doubtful Germany will meet its targets for reducing greenhouse-gas emissions in the mobility sector by 40 percent — compared with 1990 levels — by 2030, unless it takes drastic steps. 

“It doesn’t make sense to put out targets and not move anywhere near them,” said 22-year-old Luisa Neubauer, who is helping to organize the March 15 strike that, in Germany, will focus on putting pressure on the country’s transportation sector to more quickly reduce emissions. 

Germany is in the process of phasing out coal, which is the dirtiest fossil fuel and still provides about 40 percent of the nation’s electricity. Last month, Germany’s coal commission — a group of industry, environmental and government representatives — set a phaseout goal of 2038, eight years later than the date lobbied for by environmentalists. The commission’s recommendation is not binding, but it is likely to be implemented by the German government in coming years.

Phasing out coal is a hard sell in Germany. The nation’s large deposits of coal helped make it an economic powerhouse, and the industry employs about 20,000 people. Coal production also has become a political touchstone for the far-right movement and its protectionist rhetoric.

“The German politicians are very much afraid of this,” said Ortwin Renn, scientific director at the Institute for Advanced Sustainability Studies in Potsdam, Germany. “They get the support from the regions in which coal is still a major economic factor.”

But for the teenage protesters, the economic and political concerns of today are outweighed by their fears over what changes will come in the decades ahead. 

“I’m disappointed,” Blasel, the teen from Kiel, said about the 2038 announcement. “Half of the people who made the decision will be dead or retired by 2050 when the climate crisis will hit us.”

He noted that although the commission promised to include representatives from all major stakeholders, it included no youth representatives. “Every other political position will be meaningless if we don’t have an Earth to live on,” he said.

Adult leaders have voiced mixed reactions to the teens missing school to protest. 

Albert Rupprecht, a German parliamentarian and a member of the conservative Christian Social Union, part of the country’s ruling coalition, called it “completely unacceptable,” according to the news outlet Die Welt .

However, Katja Dörner, a member of the Bundestag and the environmentally progressive Green Party, sees the youth movement as a positive. “I think this sort of engagement is wonderful, and I hope that the schools will be lenient about their absence,” she said. 

It is too early to tell whether the “Fridays for Future” protests will grow into a mass movement, said Albert, the University of Bielefeld professor. The youth climate protests have not yet followed the lead of past youth-led movements such as those against the Vietnam War and apartheid, which broadened their base by incorporating related issues such as disarmament and demands for social equity, he said. 

Germany’s environmental political party, known informally as the Greens, may also benefit from the movement and incorporate some of the teens’ concerns into its agenda, especially as they reach voting age.

“I would expect that if that happens, it would give these protest movements quite a significant boost in political purchasing power,” Albert said.

For his part, Blasel said he distrusts political promises. “They say they want to do more for climate action,,” he said, “but they are not doing whatever it takes.”

Karla Adam in London contributed to this report.