Environmental campaigner Greta Thunberg has been named Time magazine’s person of the year for 2019, the publication has announced.

The Swedish teenager sparked a year of global protests on the future of the world's climate, inspiring millions of youngsters across the world to take part in strikes against the ‘climate emergency’.

READ MORE: Greta Thunberg makes plea for climate action at UN

Time made the announcement as Thunberg attended UN climate talks in Madrid.

"For decades, researchers and activists have struggled to get world leaders to take the climate threat seriously. But this year, an unlikely teenager somehow got the world's attention," the magazine wrote.

"She is an ordinary teenage girl who, in summoning the courage to speak truth to power, became the icon of a generation."

In a speech at the Cop25 talks, Thunberg hit out at world leaders' lack of ambition on climate action.

She told delegates: "Our leaders are not behaving as if we are in an emergency."

READ MORE: 'Is Greta Thunberg a time-traveller sent to save us all from disaster?'

"Countries are finding clever ways around having to take real action, like double-counting emissions reductions, and moving emissions overseas, and walking back on their promises to increase ambitions, or refusing to pay for solutions or loss and damage."

"This has to stop."

Thunberg became the youngest winner of the award  with her selection.