Greta Thunberg’s extraordinary transformation from a near-mute 11-year-old into the world’s most powerful voice on the climate crisis is revealed today by her mother.

Malena Ernman: ‘Greta was the child, we were the emperor. And we were all naked’ Read more

In an emotional account, Malena Ernman describes how her daughter came to be diagnosed with autism, and how activism helped her overcome an eating disorder.

Ernman writes of the first indications that her elder daughter was unwell in extracts published in the Observer from Our House is on Fire: Scenes of a Family and a Planet in Crisis, a book by the whole Thunberg family.

“She was slowly disappearing into some kind of darkness,” Ernman says. “She stopped playing the piano. She stopped laughing. She stopped talking. And she stopped eating.”

Ernman, a celebrated Swedish opera singer, and her husband Svante Thunberg, an actor, struggled to deal with their daughter’s silence and refusal to eat anything except tiny amounts of rice, avocado and gnocchi.

She lost 10kg in two months and was on the verge of being admitted to hospital before turning a corner. Yet when Thunberg returned to school, her father realised she was being bullied. “The school isn’t sympathetic,” Ernman writes. “Their understanding of the situation is different. It’s Greta’s own fault, the school thinks.”

After recovering some weight, Thunberg was assessed by psychiatrists and diagnosed with “high-functioning” autism, which Ernman describes as Asperger’s, as well as obsessive compulsive disorder.

She went on to become attuned to the climate crisis, with the pivotal moment coming during a film shown in class about rubbish in the oceans, “an island of plastic” in the south Pacific. But after the lesson, while Thunberg was gripped with concern, other pupils enthused about a teacher’s trip to New York and flights to Thailand and Vietnam.

“Greta can’t reconcile any of this with any of what she has just seen,” her mother writes. “She saw what the rest of us did not want to see. It was as if she could see our CO 2 emissions with her naked eye.”

In the summer of 2018, Thunberg began her first school strike, taking a homemade placard to stand outside the Swedish prime minister’s office.

When she was joined by other activists, her father tried to persuade her to go home, aware of the emotional toll it was taking on her. But she refused and the time with other people had an unexpected effect on her.

On the third day, a Greenpeace activist offered Greta some vegan Thai noodles. “She takes a little bite. And another. No one reacts to what’s happening. Why would they? … Greta keeps eating. Not just a few bites but almost the whole serving.”

Thunberg is expected to come to the UK this week to take part in a youth protest in Bristol.

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Her presence at the Bristol Youth Strike 4 Climate on Friday has been welcomed with delight by the organisers. “We are all just so excited – everyone is so excited about the thought of hearing her talk,” said Milly Sibson, who, like Thunberg, is 17. “I would love the chance to meet her because she is the founder of this movement and she is so important to it – she is an idol even though she is younger than me.”