A wave of climate change protests has swept the globe, with hundreds of thousands of young people sending a message to leaders heading for a UN summit.

Marches, rallies and demonstrations were held from Canberra to Kabul and Cape Town to New York and German police reported that more than 100,000 turned out in Berlin.

“Global Climate Strike” events ranged from 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 organisers estimated were the country’s largest protests since the Iraq War began in 2003.

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

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

And in Paris, teenagers and children 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,” Miss 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.”

Miss Thunberg is expected to participate in a UN Youth Climate Summit on Saturday and speak at the UN 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 1C since before the Industrial Revolution, and scientists have attributed more than 90% 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 heatwaves, droughts, powerful storms, flooding and other problems.

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

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

Mr Trump called global warming a “hoax” before becoming president. He has since said he is “not denying climate change” but is not convinced it is man-made or permanent.