Greta Thunberg has warned she “will not be silent when the world is on fire” as she took part in a climate strike with thousands of protesters.

The 17-year-old activist was the headline speaker at the Bristol Youth Strike 4 Climate on College Green in the city, which she said she chose to visit because the environmental movement there was “very strong”.

Avon and Somerset Police said more than 15,000 attended the event, though Greta tweeted that “at least 30,000” braved pouring rain to join her at her 80th school strike.

She took to the stage to loud chants of “Greta, Greta” before speaking for five minutes to the cheering crowd of all ages.

Greta said: “There will be a time when we will look back and ask ourselves what we did right now.

“How do we want to be remembered? This is an emergency.

“People are already suffering and dying from the consequences of the climate and environmental emergency.

“But it will get worse. And still, this emergency is being completely ignored by the politicians, the media and those in power.

“Basically, nothing is being done to halt this crisis despite all the beautiful words and promises by our elected officials.

“So what did you do during this crucial time, what will you do right now?

“Well, I will not stand aside and watch, I will not be silent while the world is on fire. Will you?

Bristol youth strike 4 climate protest
Environmental activist Greta Thunberg speaks at a Bristol Youth Strike 4 Climate protest (Ben Birchall/PA)

She took aim at world leaders, saying they were “behaving like children” in relation to the climate crisis.

“It should not be this way, we should not be the ones who have to lead on this and tell the uncomfortable truth,” Greta said.

“Once again, they sweep their mess under the rug for us young people, for their children, to clean up for them.

“But we must continue and we have to be patient and remember that the changes required will not happen overnight since the politics and solutions needed are still far from sight.

“But if enough people are pushing for change, then change will come. And we are those people. And every single person counts.”

Greta urged people to look at Bristol as an example of how such action could work.

Earlier this month, councillors on North Somerset Council’s planning committee rejected a scheme to expand Bristol Airport.

Greta Thunberg stands alongside fellow environmental activists for the Bristol Youth Strike 4 Climate protest at College Green in Bristol (Aaron Chown/PA)
Greta Thunberg stands alongside fellow environmental activists for the Bristol Youth Strike 4 Climate protest at College Green (Aaron Chown/PA)

“Activism works. So I’m telling you to act,” Greta said.

“If you look throughout history, all the great changes have come from the people.

“We are being betrayed by those in power and they are failing us but we will not back down.

“And if you feel threatened by that, then I have some very bad news for you.

“We will not be silenced because we are the change and change is coming whether you like it or not.”

The Swedish teenager, who arrived in Bristol by train, then went on to join protesters on a march through the city centre.

She walked behind a large green banner reading “Skolstrejk for Klimatet”, which translates as School Strike for Climate.

Thousands of environmental activists joined the Bristol Youth Strike 4 Climate protest (Aaron Chown/PA)
Thousands of environmental activists joined the protest (Aaron Chown/PA)

Before Greta spoke, a number of other activists gave speeches to the crowd.

Mya-Rose Craig, 17, who posts on Twitter as BirdGirlUK, called for greater diversity in the climate movement.

The teenager was the youngest person to be awarded an honorary doctorate from the University of Bristol last week.

“We have to engage with all of our communities in order to properly fight climate change,” Mya-Rose said.

“An unequal world can never be a sustainable one.”

Mya-Rose Craig was the youngest person to be awarded an honorary doctorate from the University of Bristol (Ben Birchall/PA)
Mya-Rose Craig was the youngest person to be awarded an honorary doctorate from the University of Bristol (Ben Birchall/PA)

Avon and Somerset Police confirmed that Greta had left Bristol at 3pm on Friday.

In a statement, Mike Jackson, executive director of Bristol City Council, and Superintendent Andy Bennett, Bristol Police Commander, thanked those who helped the event “run smoothly”.

They praised South Western Ambulance Service and protesters for “looking after each other”, as well as highways teams for managing a number of road closures.

“We also recognise the hard work of Bristol City Council staff and police officers and staff who pulled out all the stops to support the organisers and ensure this was a safe event for our young people,” they said.

After the march, a fundraiser was launched to repair the ground at College Green which was left muddy and without grass.

Jon Usher, who works for Sustrans, aims to raise £20,000 to restore the area ahead of spring.

“Bristol welcomed Greta Thunberg to the city for the Youth Climate Strike today and thousands turned out to see her and to stand in solidarity for climate action,” he wrote on GoFundMe.

“The weather however wasn’t on our side and it rained. A lot! And now College Green is a bit muddy. Contribute some funds to help Bristol City Council restore the grass in time for spring time picnics in the sun!”

Within hours, hundreds of people had donated and the total had exceeded £2,500.