Students around the world are missing classes to take to the streets to protest against their governments’ failure to take sufficient action against global warming.

The co-ordinated “school strikes”, being held from the South Pacific to the edge of the Arctic Circle, were inspired by 16-year-old Swedish activist Greta Thunberg, who began holding solitary demonstrations outside the Swedish parliament last year.

Since then, the weekly protests have snowballed from a handful of cities to hundreds, driven by social media-savvy students and dramatic headlines about the impact of climate change.

Greta, who was recently nominated for the Nobel Peace Prize, was cheered for her blunt message to leaders at the World Economic Forum in Switzerland this year, when she told them: “I want you to panic. I want you to feel the fear I feel every day.”

On Friday, she told a rally in Stockholm that the world faces an “existential crisis, the biggest crisis humanity ever has faced, and still it has been ignored for decades”.

“And you know who you are, you that have ignored this,” she said.

Greta Thunberg speaks at a rally in central Stockholm
Greta Thunberg speaks at a rally in central Stockholm (Henrik Montgomery/TT/AP)

Friday’s rallies are expected to be one of the biggest international actions yet. Protests were being held in cities in more than 100 countries including Hong Kong; New Delhi, India; Wellington, New Zealand; and Oulo, Finland.

– In Berlin 10,000 protesters, most of them young students, gathered in a central square waving signs with slogans such as “There is no planet B” and “Climate Protection Report Card: F”, before a march through the capital’s government quarter.

Protests in Berlin
Protests in Berlin (Michael Sohn/AP)

— In Poland, thousands marched in rainy Warsaw and other cities to demand a ban on the burning of coal. Some wore face masks as they carried banners that read “Today’s Air Smells Like the Planet’s Last Days” and “Make Love Not CO2”.

Protests in Warsaw
Protests in Warsaw (Czarek Sokolowski/AP)

— In India’s capital New Delhi, schoolchildren protested over inaction on climate change and rising air pollution levels that often far exceed World Health Organisation limits.

— “Now or Never” was among signs brandished by teenagers thronging cobblestoned streets around the domed Pantheon building which rises above the Left Bank in Paris. Several thousand students gathered peacefully around the landmark. Some targeted President Emmanuel Macron, who sees himself as the guarantor of the Paris climate accord but is criticised by activists for being too business friendly and not ambitious enough in efforts to reduce French emissions.

High school students demonstrate near the Pantheon in Paris
High school students demonstrate near the Pantheon in Paris (Francois Mori/AP)

— Police in Vienna said about 10,000 students rallied in the Austrian capital, while in neighbouring Switzerland a similar number protested in the western city of Lausanne. Last month, legislators in the northern canton of Basel symbolically declared a “climate emergency”.

— About 50 students protested in South Africa’s capital Pretoria, chanting “There’s No Planet B”. One protester held a sign reading “You’ll Miss The Rains Down in Africa”. Experts say Africa, with its population of more than a billion people, is expected to be hardest hit by global warming even though it contributes least to the greenhouse gas emissions that cause it.

Students protest outside Union Building in Pretoria
Students protest outside Union Building in Pretoria (Themba Hadebe/AP)

— In Helsinki, police said about 3,000 students gathered in front of Finland’s parliament sporting placards such as “Dinosaurs thought they had time too!”

– Danish prime minister Lars Loekke Rasmussen praised the thousands who showed up at a demonstration in Copenhagen. He tweeted: “we must listen to the youth. Especially when they’re right: the climate must be one of our top priorities. Hope all these bright young people will be back in school on Monday — we’ll need great scientists to help solve the climate issues in the future #fridaysforfuture.”

Berlin organiser Carla Reemtsma, a 20-year-old university student, said social media had been key in reaching people directly to co-ordinate the massive protests in so many different locations, noting that that she was in 50 WhatsApp groups and fielding 30,000 messages a day.

“It’s really important that people are getting together all over the world, because it’s affecting us all,” she said.

Some politicians have criticised the students, suggesting they should be spending their time in school, not on the streets.

Students in New Delhi
Students in New Delhi (Altaf Qadri/AP)

“One can’t expect children and young people to see all of the global connections, what’s technically reasonable and economically possible,” said the head of Germany’s pro-business Free Democratic Party, Christian Lindner. “That’s a matter for professionals.”

But scientists have backed the protests, with thousands signing petitions in support of the students in Britain, Finland and Germany.

“We are the professionals and we’re saying the young generation is right,” said Volker Quaschning, a professor of engineering at Berlin’s University of Applied Sciences.

“We should be incredibly grateful and appreciative of their bravery,” said Mr Quaschning, one of more than 23,000 German-speaking scientists to sign a letter of support this week. “Because in a sense, it’s incredibly brave not to go to school for once.”

A climate protest in Hong Kong
A climate protest in Hong Kong (Kin Cheung/AP)

Scientists have warned for decades that current levels of greenhouse gas emissions are unsustainable, so far with little effect.

In 2015, world leaders agreed in Paris to a goal of keeping the Earth’s global temperature rise by the end of the century well below 2C, but the world is on track for an increase of 4C, which experts say would have far-reaching consequences for life on the planet.

Mrs Merkel and French President Emmanuel Macron have publicly welcomed the student protests, even as their policies have been criticised as too limited by environmental activists.

Young demonstrators on the steps of Helsinki Cathedral
Young demonstrators on the steps of Helsinki Cathedral (Heikki Saukkomaa/Lehtikuva/AP)

In France, activist groups launched legal action against authorities this week for failing to do enough to fight climate change, citing a similar successful effort in the Netherlands.

In Germany, environmental groups and experts have attacked government plans to continue using coal and natural gas for decades to come.

Activists say that countries like Germany should fully “decarbonise” by 2040, giving less-advanced nations a bit more time to wean themselves off fossil fuels while still meeting the Paris goal globally.

Other changes needed to curb greenhouse gas emissions include ramping up renewable energy production, reining in over-consumption culture spreading beyond the industrialised West and changing diets, experts say.