Greta Thunberg may be stoutly opposed to coal mining, but was she a gold miner in a past life?

Conspiracy theorists are out in force, convinced a 120-year-old photo listed in the archives of the University of Washington's library proves the teen climate activist is a time traveller.

A black-and-white photograph of three children working a gold mine in northwest Canada in 1898 is rapidly making the rounds online.

One of the children bears a striking resemblance to the Swedish teen, convincing enough for people to run with the idea that it is in fact her.

A photo of children mining in 1898 has convinced people Greta Thunberg is a time traveller. Credit: University of Washington

Though it's mostly in jest, some say she's travelling through time to stop climate change.

"Maybe she is from the future who (sic) was sent back in time to key moments in history to stop climate change," suggested Twitter user Kelly Edwards.

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Thunberg is currently sailing to Madrid after touring the United States.

She condemned world leaders for their "betrayal" of young people through their inactivity on climate change at a United Nations summit.

Her next venture will be an appearance at the 2019 United Nation Climate Change Conference, also known as COP25, in Spain.