Tens of thousands of protesters including school students have shut down parts of Sydney and Brisbane as part of a national strike calling for action on climate change.
The Global Strike 4 Climate is taking place in 110 towns and cities across Australia on Friday, with organisers demanding a target of net zero carbon emissions by 2030 and a transition to 100 per cent renewable energy.
They are part of worldwide protests being held before leaders meet for the UN Climate Action Summit in New York next week.
In Sydney, more than 50,000 protesters took over the Domain before marching down Macquarie Street to Hyde Park.
Daniel, 15, from Fort Street High School in Sydney, said young people "are demanding more than they're being offered" from their leaders.
"Seeing how many young people are coming out, I think the current politicians we've got might not stay in power for so long anymore, with a new voting base coming in," he told AAP.
Bridget, 12, from Chevalier College in the NSW Southern Highlands, had a message for the country's politicians: "Don't be a fossil fool".
"I'm concerned about this because I kind of want a future," she said.
"They didn't do anything when they were kids so they left it all up to us to fix."
In Brisbane, thousands filled Brisbane's Queens Gardens to capacity, with columns of protesters spilling out and closing part of George Street in the CBD.
Lucy McDougall, from Mountain Creek State High School on the Sunshine Coast, should have been sitting a exam on Friday.
"I should be sitting in a chemistry exam today, and it's a significant one. Of course I'm concerned about missing that," the 16-year-old told AAP.
"But this is more important.This is a crisis and it's our future at risk.
She had a pointed message for Prime Minister Scott Morrison.
"He's going to die sooner than we are. This is our future. Start making choices that benefit us."
Global Strike 4 Climate organisers expect a 50 per cent increase in attendance from the most recent climate strike in March, which drew 150,000 protesters.
Universities have confirmed they will not penalise students for attending the rallies, while the Uniting Church synod for NSW and the ACT have backed their students to attend the demonstrations.
But Catholic and Anglican church-run schools say their students should remain in class, as do NSW public schools.
Acting Prime Minister Michael McCormack said students should be in school.
"I think these sorts of rallies should be held on a weekend where it doesn't actually disrupt business, it doesn't disrupt schools, it doesn't disrupt universities," Mr McCormack told reporters in Melbourne.
"I think it is just a disruption."
The strike is the latest in a worldwide movement started in August 2018 when 16-year-old Swedish climate activist Greta Thunberg began protesting outside Sweden's parliament on school days.
She'll participate in the UN's youth climate forum on Saturday and address world leaders at the UN secretary-general's climate summit on September 23.
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