They might not seem like your typical revolutionaries but for the past few months they've been putting themselves on the line to call for urgent action on climate change. Urgent being the operative word.

Almost a year ago, scientists put the world on red alert - according to the latest IPCC report there was just over a decade left to radically curb our carbon emissions to keep the world below 1.5 degrees of warming. Any higher, and the UN predicts hundreds of millions more people will suffer under increased heatwaves, disease, food and water shortages, coastal flooding and monster storms.

In the months following that grim forecast, Extinction Rebellion emerged suddenly into the spotlight.

Over 11 days in April, activists holding signs and banners bearing the "XR" hourglass symbol scaled bridges, blockaded roads and shut down much of London. A mural by renowned street artist Banksy appeared overnight, depicting a girl with the XR sign and the words "From this moment despair ends and tactics begin". Days later, a UK parliament under pressure declared a climate emergency. And XR spread to more than 70 countries across the globe.

Now the rebellion is here in Australia, in our peak hour traffic, to "disrupt business as usual". From sombre funeral processions to carnival-style street protests, students and grandparents dressing up as bees to farmers, tradies and public servants gluing themselves to roads, XR is loud, colourful - and growing.

The group shares members in common with the Global Climate Strike that's seen hundreds of millions walk out of classrooms and workplaces in recent months, but it's decidedly more adult - drawing on the legacies of Mahatma Gandhi, the suffragettes and Martin Luther King's civil rights movement to take peaceful protest into nonviolent civil disobedience.

And, perhaps to no one's surprise, it's making plenty of enemies in the process. Members have been likened to a doomsday cult and branded as extremists, dole-bludgers and "crusties" by conservatives.

Here in Australia, amid mounting commuter frustration, there's been calls for tougher penalties and police crackdowns, and a raft of new laws are being fast-tracked already in Queensland, as protesters face "draconian" bail conditions - and even library bans. Some veteran activists have themselves raised concerns that XR's wilder tactics are only polarising people further on climate change.

So will the rebellion fizzle out in a traffic jam or are we witnessing the birth of a historic social movement?

On Thursday, the eve of another planned "disruption" in Canberra, organisers shook their heads at suggestions XR was alarmist or aggressive.

"We're just normal people," said local designer and first time activist Margaret. "A lot of us are professionals. We understand how economies work. But we also understand the science."

Two high-profile die-ins have now shut down parts of the capital this month - with another planned for Friday at 5.30pm - as part of a fortnight of global "rebellion". Hundreds have now been arrested across Australia (though so far none in Canberra). While some protesters are willing to break the law to jolt governments into climate reform, organisers insist not everyone has to face arrest to join.

Terry, an electrician by trade, admitted he still felt "a bit naughty" taking part in his first act of civil disobedience at the "die-in" with this wife and kids on Commonwealth Bridge last week.

"You're sort of hard-wired to not disobey," he said. "But the police were happy, people were waving and giving us the thumbs up, very rarely would someone have a go."

"You can feel like it's not doing much, but you can talk yourself into doing nothing too. We'll keep going...it's good for the soul."

Having served two combat tours with the US army, Jeremy Michael said he held real fears for the future - and for his young son.

"I know how truly terrible war can be [and] I think future wars over resources like water will make previous wars look like schoolyard squabbles," he said.

Esther Marsh said contemplating the life ahead for her own young son, Monty, had also brought the crisis crashing down on her.

"I'd just stay up at night worrying about him," she said. "I realised I had to do everything I could to ensure he had a safe planet. It feels powerful being part of this, even if it's not changing anything right now."

Former public servant Leo Bild admitted activism is not what he had planned when he retired in July.

"This just seems the most urgent issue of our time," he said. "If you're a little bit late to work, that's nothing compared to the disruption climate change will bring. We try to be as polite as we can."

To XR, extinction doesn't just mean the millions of species vanishing around us as the world enters its sixth mass extinction event - it also means us - or at least our current way of life.

"The third world war - of profit versus life - is already underway. Humanity itself is on the brink of the abyss," its website declares.

It's sobering reading - and many have accused environmental protesters of unduly spreading fear, including among school kids.

But the UN, human rights organisations, even some scientific papers, have been using their own alarming rhetoric for decades as the research revealed an increasingly grim picture.

Now, in a world already more than one degree warmer than it was before the industrial revolution, experts warn the full force of climate change will radically destabilise world economies and governments unless they transition to renewable energy soon.

While actual human extinction seems unlikely, the UN has warned of a "climate apartheid" where only the rich can afford to escape the worst effects of a changing climate.

Hundreds of Australian academics have now signed an open letter supporting the rebels, declaring the federal government's inaction on the climate crisis has already broken the social contract - leaving people with both the right and the "moral duty to rebel to defend life itself".

The demands of the rebellion are similar around the globe - they want governments to declare a climate emergency and bring in reform that fits the urgency of the problem, similar to the mobilisation the world saw at the outbreak of WWII. A key part of that is the creation of a citizen's assembly to oversee a fair transition for workers and communities and ensure transparency.

Their deadlines are steep - governments must halt biodiversity loss and cut emissions to net zero by 2025. While there is still some debate within the scientific community about how time we have left before we blow our "carbon budget", experts agree ambitions need to grow - fast.

For all its radical branding, the rebellion started with something shockingly ordinary - academia. Organisers in the UK drew on research which found sustained resistance from just 3.5 per cent of a population was enough to topple dictatorships and trigger societal change - and that non-violent campaigns were the most effective.

"People have been trying for decades to go through the proper channels, writing to politicians, signing petitions, marching," Bild said. "Nothing's happened."

XR has instead turned to a playbook of successful historical campaigns - from the suffragettes to the anti-war protests of the 70s - to grab headlines and cause disruption.

They're blocking roads, scaling buildings, plastering buildings with fake blood, even marching nude. Some of their tactics, such as locking onto mining equipment or landmarks, has drawn particular criticism. In the UK, XR organisers distanced themselves from a plan to disrupt Heathrow Airport with drones over concerns about the methods used.

But the movement is largely without hierarchy - local members organise in "affinity groups" with like-minded people or those nearby, working with police, planning actions and coordinating across social media.

"Some of us are teachers and public servants so a lot of it's taking minutes, it's quite bureaucratic," laughed one organiser.

"Us adults are a bit less out there than the student groups."

Gerard De Ruyter, another former public servant and father of two, said he had long been an environmentalist but this was his first big foray into activism. That includes dressing the part - he and Margaret are among the key organisers of the Red Rebels, a sub-group of XR that wear stark red robes and white masks. Silent but "emotive", they move like a Greek chorus, symbolising the grief - and the blood - of all species lost to extinction.

"We rehearse, but once we put on that costume, it's almost like a trance," Margaret said. "You almost become anonymous, you become a Red Rebel.

"That's part of what's been so powerful about this for me. I got tired of just screaming at the TV. There's something in coming together to [express] and share our grief for what's happening."

"People stand and just watch us," De Ruyter said. "It takes me back to my student theatre days. It seemed like a chance to do a bit more than just holding up signs."

But while he cautions against turning protests into a circus, others stress comedy rather than tragedy should play a larger role in welcoming new people into the fold.

Kim Stern is one of the key organisers of the student arm of XR in Canberra - a group made up school student strikers as well as those at university. He admits they have a particular flair for the theatrical - having just dressed up as a construction crew and tried to dig a new coal mine on the front lawn of the Minerals Council of Australia in Canberra on Thursday morning.

"You know, shockingly, as good as it would have been for jobs and growth, they said we couldn't build another coal mine," he laughed. "That must be the first time the council hasn't been lobbying for new coal.

"Some people really like the XR funeral processions. I see why but I don't know if that translates into the joy and the courage you need to build a movement.

"Saving the planet can be a lot of fun."

Organisers admit the movement has also copped criticism for reflecting mostly white, middle class values - and a perceived demand that people of colour face down police and brave arrest.

"I think that's alienated some people," Stern said.

Leo Bild agrees XR could do more to connect with Indigenous communities and De Ruyter says he is hopeful more talks are about to get underway.

So far Canberra activists don't expect to see the "rough and tumble" of police crackdowns elsewhere in the world. As their numbers grow, they are keeping just ahead of authorities, walking a fine line between civil disobedience and law-breaking.

"We don't want to all get locked up too early," laughs Bild.

Still, all XR members are trained on what to expect during direct action and how to behave.

"You can't just bring a can of beer along," Gras explains.

Indeed, for a group without a clear hierarchy, Jeremy Michael says it was XR's research and organisation that sold him on joining.

"About [ten years ago] I was a little bit of a climate sceptic," he admits. "I wasn't totally convinced of how scary it was. I was fresh out of active duty military, which has quite a conservative leaning.

"But XR are using great historical examples of where this has worked before and how they did it back then. They kept going. People have short memories of that now."

Michael says that while standing in a crowd at a rally can at once feel powerful and pointless, being part of XR felt "more serious" than previous protests he had joined.

"It does feel good to be fighting for it right here in Canberra where the politicians can really hear it and feel it.

"I feels like this is really becoming a movement. I feel swept up in it.

"They've got a plan."

So far, no one is showing any sign of slowing down. More disruptions are planned for Canberra and elsewhere - including federal parliament - in the weeks and months ahead. But growing unrest, such as attacks on two protesters in London by angry commuters overnight, is sparking concern.

While Bild notes XR is still a young movement and non-violent, he admits it's unclear where it will go if it builds up enough steam to deliver seismic change.

"It's not called a rebellion for nothing."

Extinction Rebellion will meet at Garema Place in Canberra at 5:30pm tonight ahead of more planned disruptions.