Greta: the voice of climate activism who says 'listen to the scientists'

She's the voice of a global movement who mobilised millions of young people to demand action against climate change. Yet Greta Thunberg's message to the US Congress - a hotbed of climate scepticism - was:

Little more than a year ago, we hadn't heard of Thunberg. That changed after August 2018 when she held her first skolstrejk för klimatet, a 'school strike for climate', ducking out of class to protest outside Sweden's parliament.

Before long others joined her school strikes and, within a matter of months, a global movement was born. By March 2019, more than 2 million students across 135 countries were holding school strike demonstrations.

Thunberg has come a long way in a year, both literally and figuratively. In October she was awarded the 2019 Nordic Council Environment Prize, but turned it down because "the climate movement does not need any more awards," she said on Instagram.

She went on to say there is "no lack of bragging" about the Nordic countries' green credentials, but that "when it comes to our actual emissions and our ecological footprints per capita - if we include our consumption, our imports as well as aviation and shipping - then it’s a whole other story."

Just weeks after her 16th birthday she attended the World Economic Forum’s Annual Meeting in Davos, where she famously urged world leaders to “panic” at the seriousness of the situation.

“I don’t want your hope,” she told the audience. “I want you to panic. I want you to feel the fear I do. Every day. And want you to act. I want you to behave like our house is on fire. Because it is.”

In March Thunberg was nominated for a Nobel Peace Prize. Time magazine named her one of the world's most influential people and put her on its cover. She has addressed the European Parliament, the French National Assembly, the UK's House of Commons, and met with Pope Francis.

Then in September she is addressed the United Nations Climate Summit in New York, a meeting she travelled to by carbon-neutral yacht.

“It is insane that a 16-year-old would have to cross the Atlantic to take a stand," she told reporters on arrival at the harbour. "The climate and ecological crisis is the biggest humanity has ever faced.”

And on the eve of the UN summit, she spearheaded an unprecedented global demonstration calling for action on climate change.

Sukhman Dhami, 41, who joined the New York leg of the protest, told Reuters: “Scientists establish the facts, but it’s up to communities and people to demand everyone act on this.

“Greta Thunberg has inspired millions of Gretas - young and old.”

After New York she travelled back across the 'pond' - again by boat - to attend COP25 in Madrid, before being named TIME's 2019 Person of the Year.

Greta rounded off 2019 with a Skype conversation with Sir David Attenborough, the long-time documentary filmmaker and activist. He praised Greta’s energy and commitment, saying she had done more in less than two years than others had in two decades: “She’s achieved things that many of us who’ve been working on it for 20 odd years have failed to achieve," he said.

“I’m very grateful to you. You have woken up the world.”

She, in turn, cited Attenborough’s rich legacy of documentaries about the natural world as a source of inspiration: “When I was a young girl, documentaries about the natural world and what was happening, and what was going on, that was what made me realise the situation.

“So thank you for that. That’s what made me decide to do something about it.”

Later this month, Greta returns to Davos for the World Economic Forum Annual Meeting. “I don’t know why people are listening to me,” she said during her chat with David Attenborough. “And I don’t know how long it will last. I just know right now people are listening. I need to use that opportunity.”