World / Massive 60-foot tall mural of Greta Thunberg stares down at San Francisco

A massive portrait of Greta Thunberg gazed down onto San Francisco on Tuesday night after an artist unveiled a mural of the Swedish teen activist in a bid to remind residents of the dangers posed by climate change.

The 60-foot tall, 30-foot wide (18-by-9 meter) mural was revealed hours after Thunberg announced on Twitter that she would be leaving the United States by boat on Wednesday, headed for a United Nations climate change conference in Madrid in December.

The teenager rejects air travel because of its high levels of greenhouse gas emissions.

Argentine street artist Andres Petreselli, who signs his work Cobre, said that the portrait of Thunberg, 16, was unusual because he typically does not address politics, religion or sports.

"But, this one is ... I feel connected with the politics behind (it) because I think it is real and if I have to compare it with the rest of my murals, this is the most political one that I ever made," the 32-year-old said as he sat on a roof with the mural behind him.

Petreselli previously painted a since-demolished mural of the late actor Robin Williams in San Francisco.

Paul Scott, the executive director of OneAtmosphere.org, the San Francisco nonprofit that funded the work, said he hoped passers-by would be "touched" by the image of Thunberg, who has mobilized a global youth movement against climate change.

"We are really just hoping that it stops and makes them think, that this will amplify Greta's message, that people will start to understand the clear call for action that she is sending out," Scott said.

Thunberg has spent the last three months in North America after arriving in New York City by boat on August 28, delivering a speech at a United Nations climate summit there in September.

In her Twitter post on Tuesday she said she would set sail from Virginia in the morning on a 48-foot catamaran whose owners have offered her a ride across the Atlantic.