NEW YORK (AP) — A wave of climate change protests swept the globe Friday, with hundreds of thousands of young people sending a message to leaders headed for a U.N. summit: The warming world can’t wait for action.

Marches, rallies and demonstrations were held from Canberra to Kabul and Cape Town to New York.

The “Global Climate Strike” events ranged from a gathering of about two dozen activists in Seoul using LED flashlights to send Morse code messages calling for action to rescue the earth to Australia demonstrations that organizers estimated were the country’s largest protests since the Iraq War began in 2003.

“Basically, our earth is dying, and if we don’t do something about it, we die,” said A.J. Conermann, a 15-year old high school sophomore among several thousand of young people who marched to the Capitol building in Washington.

“I want to grow up. I want to have a future,” Conermann added.

In New York, where public schools excused students with parental permission, tens of thousands of mostly young people rallied and marched through lower Manhattan.

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

And 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 protests 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 is 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, powerful storms, flooding and other problems, and that some have already started manifesting themselves.

Climate change has made record-breaking heat temperature records twice as likely as record-setting cold temperatures over the past two decades in the contiguous U.S., according to National Oceanic and Atmospheric Administration data.

Nations around the world agreed at a 2015 summit in Paris to hold warming to less than 2 degrees Celsius (3.6 Fahrenheit) more than pre-industrial-era levels by the end of this century.

But U.S. President Donald Trump subsequently announced that he was withdrawing the U.S. from the agreement, which he said benefited other nations at the expense of American businesses and taxpayers.

Trump called global warming as a “hoax” before becoming president. He has since said he’s “not denying climate change” but is not convinced it’s manmade or permanent.

New York 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. Because someone needs to do it.” At least one Trump supporter waved a large “Trump 2020” flag as the demonstrators marched in Manhattan.

Friday’s demonstrations started in Australia, where organizers estimated 300,000 protesters marched in 110 towns and cities, including Sydney and the national capital, Canberra. Demonstrators called for their country, the world’s largest exporter of coal and liquid natural gas, to take more drastic action to reduce greenhouse gas emissions.

Acting Prime Minister Michael McCormack — filling in while Prime Minister Scott Morrison was on a state visit to the United States — said Australia was already taking action to cut emissions. McCormack called the climate rallies “ a disruption” that should have been held on a weekend to avoid inconveniences.

Many middle schools in largely coal-reliant Poland gave students the day off so they could participate in the rallies in Warsaw and other cities, and President Andrzej Duda joined school students picking up trash in a forest. German police said more than 100,000 people gathered in front of Berlin’s landmark Brandenburg Gate, near where Chancellor Angela Merkel’s Cabinet thrashed out the final details of a 54 billion euro ($60 billion) plan to curb Germany’s greenhouse gas emissions .

Thousands of schoolchildren and their adult supporters demonstrated in London outside the British Parliament, some holding placards with slogans including “Don’t be a fossil fool” and “Make our planet Greta again,” in a reference to Thunberg.

The British government said it endorsed the protesters’ message but didn’t condone skipping school — a stance that didn’t sit well with some of the young protesters.

“If politicians were taking the appropriate action we need and had been taking this action a long time ago when it was recognized the world was changing in a negative way, then I would not have to be skipping school,” said Jessica Ahmed, a 16-year-old London student.

In Helsinki, the Finnish capital, a man dressed as Santa Claus stood outside parliament holding a sign: “My house is on fire, my reindeer can’t swim.”

Smaller protests took place in Asia, including in Japan, South Korea, the Philippines, Hong Kong and India.

“We need to reclaim our constitutional right to clean air and water,” said Aman Sharma, a 16-year-old protester in India’s capital of New Delhi.

In the Afghan capital, Kabul, an armored personnel carrier was deployed to protect about 100 young people as they marched, led by a group of several young women carrying a banner emblazoned with “Fridays for Future.”

“We know war can kill a group of people,” said Fardeen Barakzai, one of the organizers. “The problem in Afghanistan is our leaders are fighting for power, but the real power is in nature.”

In Africa, rallies were held in Johannesburg and the South African capital, Pretoria, as well as Kenya’s capital, Nairobi, where some young protesters wore hats and outfits made from plastic bottles to emphasize the dangers of plastic waste, a major threat to cities and oceans.

Africa is the most vulnerable continent to climate change and the least equipped to deal with it, experts have said. Governments have pleaded for more support from the international community.

Climate change “is worse than homework,” one sign proclaimed.