NEW YORK (AP) — Young people afraid for their futures protested around the globe Friday to implore leaders to tackle climate change, turning out by the hundreds of thousands to insist that the warming world can’t wait any longer.

Marches, rallies and demonstrations were held from Canberra to Kabul and Cape Town to New York. More than 100,000 turned out in Berlin.

Days before a U.N. climate summit of world leaders, the “Global Climate Strike” events were as small as two dozen activists in Seoul using LED flashlights to send Morse code messages and as large as mass demonstrations in Australia that organizers estimated were the country’s largest since the Iraq War began in 2003.

“You are leading the way in the urgent race against the climate crisis,” U.N. Secretary General António Guterres wrote in a message to the young protesters on Twitter. “You are on the right side of history. Keep pushing us to do the right thing.”

In New York, where public schools excused students with parental permission, tens of thousands of mostly young people marched through lower Manhattan, briefly shutting down some streets.

“Sorry I can’t clean my room, I’m busy saving the world,” one protester’s sign declared.

Thousands marched to the Capitol in Washington, including 15-year-old high school sophomore A.J. Conermann.

“Basically, our earth is dying, and if we don’t do something about it, we die,” Conermann said.

Thousands packed the streets around Seattle’s City Hall, following a march where tech workers from Amazon and Google joined students demanding an end to fossil fuel use.

Demonstrations came in smaller cities as well. Washington Gov. Jay Inslee, who recently abandoned his climate-focused presidential run, addressed a rally in Spokane, and a crowd chanted inside the rotunda of the state Capitol in Madison, Wisconsin.

“It’s really unbelievable and really startling to know how little time we have to reverse the damage,” said Maris Maslow-Shields, a high school student from Santa Rosa, California, who marched in San Francisco.

In Paris, teenagers and kids as young as 10 traded classrooms for the streets. Marie-Lou Sahai, 15, skipped school because “the only way to make people listen is to protest.”

The demonstrations were partly inspired by the activism of Swedish teenager Greta Thunberg, who has staged weekly “Fridays for Future” demonstrations for a year, urging world leaders to step up efforts against climate change.

“It’s such a victory,” Thunberg told The Associated Press in an interview in New York. “I would never have predicted or believed that this was going to happen, and so fast — and only in 15 months.”

Thunberg spoke at a rally later Friday and was expected to participate in a U.N. Youth Climate Summit on Saturday and speak at the U.N. Climate Action Summit with global leaders on Monday.

“They have this opportunity to do something, and they should take that,” she said. “And otherwise, they should feel ashamed.”

The world has warmed about 1 degree Celsius (1.8 Fahrenheit) since before the Industrial Revolution, and scientists have attributed more than 90 percent of the increase to emissions of heat-trapping gases from fuel-burning and other human activity.

Scientists have warned that global warming will subject Earth to rising seas and more heat waves, droughts, storms and flooding, some of which have already manifested themselves.