Swedish climate activist Greta Thunberg has taken her disarmingly straightforward message -- "listen to the scientists" -- around the world. (AFP)

Greta Thunberg, the Swedish teenager who became the voice of a generation facing the climate change emergency, was Wednesday named Time magazine’s 2019 Person of the Year.

Unknown to the world when she launched a solo strike against global warming in mid-2018, the 16-year-old has since inspired millions in a worldwide movement that saw her tipped as a Nobel laureate.

“Wow, this is unbelievable!” Thunberg tweeted after the announcement—which came as she pressed her call for action at a high-stakes UN climate gathering in Madrid.

“I share this great honor with everyone in the #FridaysForFuture movement and climate activists everywhere.”

The magazine interviewed Thunberg aboard the sailboat that took her from the United States back to Europe, after a months-long journey through North America aimed at raising environmental awareness.

“We can’t just continue living as if there was no tomorrow, because there is a tomorrow. That is all we are saying,” Thunberg told Time.

“The politics of climate action are as entrenched and complex as the phenomenon itself, and Thunberg has no magic solution,” Time wrote of the teenager.

“But she has succeeded in creating a global attitudinal shift, transforming millions of vague, middle-of-the-night anxieties into a worldwide movement calling for urgent change.

“She has offered a moral clarion call to those who are willing to act, and hurled shame on those who are not.”

Within months of launching her lonely “School Strike for the Climate,” or “Fridays For Future,” protest outside the Swedish parliament, Thunberg was spearheading global youth demonstrations and demanding environmental action from decision-makers around the world.

“I want you to panic,” she told CEOs and world leaders at the annual World Economic Forum in Davos Switzerland on January 2019. “I want you to feel the fear I feel every day. And then I want you to act.”

The daughter of an opera singer mother and an actor-turned-producer father, Thunberg has faced severe criticism — the latest from Brazilian President Jair Bolsonaro, who dismissed her as a “brat” — and been the subject of a swarm of online conspiracy theories.

Some have mocked her youth — or sought to discredit her because she has Asperger’s syndrome, a mild form of autism.

Her diagnosis means that Thunberg “doesn’t operate on the same emotional register as many of the people she meets,” Time magazine wrote.

“She dislikes crowds; ignores small talk; and speaks in direct, uncomplicated sentences. She cannot be flattered or distracted,” and according to the magazine, “these very qualities have helped make her a global sensation.”

Thunberg has been mystified by the hostility she sometimes faces.

“I honestly don’t understand why adults would choose to spend their time mocking and threatening teenagers and children for promoting science when they could do something good instead,” she said in September.

Thunberg says she has received no money for her activism, but with 12 million followers across her Instagram, Twitter and Facebook accounts, she continues to rack up high-profile supporters, from Barack Obama to the Dalai Lama and Arnold Schwarzenegger.

“No one is too small to have an impact and change the world,” tweeted The Obama Foundation as it welcomed the Time announcement.

Democratic White House hopeful Joe Biden echoed that sentiment, saying the “honor is well-deserved and serves as a reminder of the urgent, drastic action we must take to address the climate crisis.”

“I couldn’t think of a better Person of the Year,” agreed former secretary of state Hillary Clinton, thanking Thunberg for her “willingness to tell hard, motivating truths.”