The 16-year-old’s lone protest last summer has morphed into a powerful global movement challenging politicians to act.

Greta Thunberg is hopeful the student climate strike on March 15 can bring about positive change, as young people in more and more countries join the protest movement she started last summer as a lone campaigner outside the Swedish parliament.

The 16-year-old welcomed the huge mobilization planned in the UK, with demonstrations by tens of thousands of school and university students in Australia, Belgium, Germany, the United States, Japan, and more than a dozen other countries.

“I think enough people have realized just how absurd the situation is. We are in the middle of the biggest crisis in human history and basically nothing is being done to prevent it. I think what we are seeing is the beginning of great changes and that is very hopeful,” Thunberg wrote in a social media post.

Thunberg has risen rapidly in prominence and influence. In December, she spoke at the United Nations climate conference, berating world leaders for behaving like irresponsible children.

Last month, she had similarly harsh words for the global business elite at Davos. She said: “Some people, some companies, some decision-makers in particular, have known exactly what priceless values they have been sacrificing to continue making unimaginable amounts of money. And I think many of you here today belong to that group of people.”

The movement she started has morphed and grown around the world and, at times, linked up with older groups, including Extinction Rebellion, 350.org and Greenpeace. Next week she will take the train to Brussels – having decided not to fly due to the high carbon emissions of aviation – to speak at an event alongside Jean-Claude Juncker, the president of the European commission.

She then travels on to Paris to join the school strikes now expanding in France. Veteran climate campaigners are astonished by what has been achieved in such a short time.

“The movement that Greta launched is one of the most hopeful things in my 30 years of working on the climate question. It throws the generational challenge of global warming into its sharpest relief, and challenges adults to prove they are, actually, adults. So many thanks to all the young people who are stepping up,” said Bill McKibben, the founder of 350.org.

Around the world, so many student strikes are now taking place or planned that it is becoming hard to keep up. Supporters have compiled a Google map that pins all the reported or announced locations, stretching from Abuja and Bugoloobi to Sacramento and Medellín.

More than 3,000 scientists have given their backing to the strikes. Some European governments are clearly feeling the pressure. The environment minister was forced to resign after falsely claiming the country’s intelligence services held evidence that the striking children were being directed by unnamed powers. The allegation was quickly contradicted by intelligence chiefs.

Activists said they want to make clear that the problem is systematic rather than a matter of individual lifestyle choices. They have been criticized by right-wing politicians, but local governments have met student delegations to discuss short-term steps, such as a ban on any school trip that involves a flight. One regional authority has declared its support for the student movement. In an election year, state leaders have also expressed guarded support.

The global strike on 15 March is expected to be the biggest yet with mobilizations in 150 cities. “It is not acceptable that grown-ups are destroying the future right now,” said Jakob Blasel, a high-school student. “Our goal to stop coal power in Germany and fossil energy everywhere.” He said politicians have expressed admiration for their campaign, but this has not translated into action. “This is not acceptable. We won’t stop until they start acting.”

Until now 75% of the participants have been schoolchildren but increasing numbers of university students are joining. Luisa Neubauer, a 22-year-old, was among those invited to talk to senior cabinet officials. She told the German minister of economy that he was part of the problem because he was working for industry, rather than for people or the planet.

“What we need our politicians and our government to understand is that everything they do today comes at a price for future generations,” Neubauer said. “We are not doing this for fun, but because we don’t have a choice.”

But she too noted a new direction in the national discussion. “There is a debate now about climate and the environment, which is good. People for the first time in years are not talking about refugees but talking about the environment.”

Jonathan Watts

Michael Campanella

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