Everything you need to know about today's climate strike - and why it matters

Today, three days out from another crucial UN summit in New York, young people will lead what is expected to become the largest global climate protest in history.

The UN secretary general says he's counting on them to compel governments to act in line with the science of global warming (i.e fast). As the window closes to prevent runaway climate change, academics, doctors, unions, churches, businesses, even some governments, have also thrown their support behind the protests.

Many workers and university students will take the day off to join marches across the globe, including here in Canberra where 10,000 are expected to pack out the city.

The School Strike 4 Climate movement started almost exactly a year ago with a Swedish teenager named Greta Thunberg. The sixteen-year-old started skipping school each Friday to camp out the front of her own country's parliament in protest over climate inaction.

Inspired by her stance, school students organised similar "strikes" the next month in more than 20 other countries. Record crowds came out again in force in March this year - drawing more than 5000 to Canberra, 150,000 Australia-wide and an estimated 1.5 million globally.

Greta has since been nominated for a Nobel Peace Prize and addressed world leaders, including at the UN. She continues to strike regularly and says her grades are still strong.

While all the strikes have drawn attention so far, this time around students have refined their demands. In Australia, they want the federal government to commit to:

For student strikers, almost every year of their life has ranked among the hottest on record. As he painted his sign for the protest this week, eight-year-old Sebastian Grey from Googong explained his fears for the future.

"I'm really scared, what happens when I'm 58?" He says. "[Politicians] need to start listening to us now, this year."

The strikes are run by local student groups and largely organised over social media - from Facebook to the slightly surreal lip-syncing app TikTok. But there's also been plenty of old-fashioned door to door campaigning, 12-year-old Arianne from the Canberra chapter says.

"I went up and down Northbourne telling people about the strike for two days," she said. "We went to our principal and put on a special assembly so people knew."

Environmental groups including Greenpeace, 350.org, the Australian Conservation Foundation and the youth-run Australian Youth Climate Coalition have also lent a hand - donating supplies, running safety training and walking students through obtaining police permits. This time around, they've been more involved - as workers and university students also prepare to march - which has fuelled allegations left-wing lobby groups are the secret masterminds of the movement, exploiting and scaring kids out of their classrooms.

But the students themselves insist they are still very much running the show.

In the final planning meeting on Wednesday, 17-year-old Tahli said the last Canberra strike had been a "mad scramble", with students largely working without adult guidance.

"We were trying to sort stuff out right up til the night before," she said. "There were so many things we hadn't thought about."

This year, student organiser Aoibhinn Crimmins says they've had more help - but there's also a much bigger crowd to look after.

"There's so much construction in the city right now, we've even had people calculating how many people a second can pass through certain tight spots on the march route," she said. "We've got a lot of older people coming, people [with mobility issues]. There's so much to do."

READ MORE: What it's really like running a climate movement after school

At Greenpeace Australia Pacific, Dom Rowe said even seasoned campaign veterans were learning a lot from the students.

"They're inspiring us and I think they're inspiring themselves too as they're going along," she said.

Many parents and principals are backing strikers given the urgency of what many are now calling the climate emergency.

"We are the last generation that can save the planet," student strikers say. And scientists agree.

Scores of reports, including from the UN, now warn we have entered the deciding decade - a radical overhaul of our emissions-intensive economy is needed in the next few years to stop temperatures rising above 1.5C this century. That target in itself will still bring major problems as countries battle climate-related migration and health problems alongside more intense storms and fires.

Sydney private school headmaster Michael Parker opposed the strike at first but a meeting with a group of Year 11 students soon changed his mind.

In a letter that has since gone viral, he told parents: "Going on a march for climate fits the school's vision better than one more regular day around the classrooms, they tell me.

"I'd rather they went away. I'd rather get back to the school's strategic plan and the council retreat. But these kids are passionate, they are smart and they have thought it through...Students who have shown they care about this should be able to march about it. If their parents have allowed them to be absent to go to the strike, then the least we can do is give them the school's support too. Damn these Year Elevens. Because they're right."

But in striking, students have defied Prime Minister Scott Morrison, who has called for less activism and more learning in schools, and stepped into a storm of criticism - and even ridicule - led by some Coalition MPs.

Liberal backbencher Craig Kelly sensationally declared students were being fed climate lies in parliament this week, challenging the vast body of research behind man-made global warming which has now been backed by 99 per cent of the world's scientists.

But it's been a different story at the local ACT government level, which is closing in on plans to source 100 per cent of its electricity from renewables by next year. The government, led by Education Minister Yvette Berry, invited student strikers to speak at the assembly this week and has encouraged schools to organise excursions to the protests.

The education directorate says no student with parental permission to strike will be penalised but teachers seeking to join them outside a formal excursion will need to attend on their lunch break or apply for leave.

While ACT public servants have been given the all clear to strike, the federal government has warned Commonwealth staff not to walk off the job.

Australia's emissions are continuing to rise and the Morrison government says it does not plan to change its targets or climate policy.

While some argue Australia is a small player on the world stage, it's also a big exporter of fossil fuels - the main contributor to escalating man-made climate change. Up north, experts warn the government's approval of the Adani mine - which will open up one of the last untapped coal reserves on the planet - could torpedo global efforts to curb emissions even though most of the coal will be burnt overseas and so not counted towards Australia's international carbon credits.

"It's really a climate bomb," chief executive of the Australian Conservation Foundation Kelly O'Shanassy says. "But Australia we're a sunny, windy country, we also have this huge potential to become the biggest exporter of renewables."

Like many campaigners, she said the student strikes marked a shift in public opinion - as children led their parents and teachers and communities from climate concern to climate action.

"These strikes are a real game-changer because we're seeing kids who are afraid for their future speaking out and their parents are joining in, their communities are joining in. And the signs! I love the signs."

Australia's former chief scientist Penny Sackett agrees the strikes could be more effective than 25 years of UN climate summits.

Student organisers say part of the power of today's strikes is the huge presence of workers and unions - a sign the old dichotomy between the economy and the environment no longer holds water.

In fact, at 350.org Glen Klatovsky says the business case for a rapid shift to renewable energy has now eclipsed the old coal and gas industries. And companies and super funds have started to move their money accordingly.

"About $11 trillion has already been committed for divestment around the world, that's companies and local councils, even [the ACT government] and the nation of Ireland," Mr Klatovsky said.

"It's working, last year Shell Oil revealed in its annual report that it was having a hard time attracting investment in its projects...And now we're seeing these young people coming out, it's wonderful."

Among those calling on Australian super funds and companies to divest is Daramalan College student Kate Grimwood. She's been advocating for Australia's $200 billion wealth fund, the Future Fund, to reveal where it's investing the country's savings.

"I won't lie, juggling studies and campaigning wasn't and still isn't easy, but the school has helped me immensely," she said. "Getting involved....is one of the best feelings I've ever had."

There are strikes planned all across Australia - from cities to regional towns. In Canberra, strikers will gather at Glebe Park in Civic at 12pm before marching just after 1pm through the city and back.

You can find your closest protest at www.schoolstrike4climate.com

Head to our rolling coverage of the strike here for a picture gallery. If you're particularly proud of your own sign, send us a photo at sherryn.groch@canberratimes.com.au