Tens of thousand of Australians have turned out for climate change rallies across the nation, calling on the Abbott Government to keep the carbon tax.

The National Day of Climate Action was organised by activist groups including GetUp!, the Australian Youth Climate Coalition and the Australian Conservation Foundation.

Organisers say about 60,000 participated at the rallies, which were held in capital cities and more than 130 towns and regional centres.

Emergency workers played a significant role in warning about the dangers of unchecked global warming, while Labor and Greens politicians, along with climate scientists, also participated.

The Climate Council's Tim Flannery told 30,000 people in Melbourne that Australians must make their voices heard.

"The simple truth is this: that we cannot leave a matter as important as climate change to the fickleness and whim of Australia's politicians," he said.

"We must stand up and be counted [and take] every effort to speed the uptake of renewable energy."

Greens deputy leader Adam Bandt evoked the memory of the 2009 Black Saturday bushfires, while firefighters spoke of their fears of increasingly hotter days.

"There is no sceptic at the end of a fire hose," said Peter Marshall, secretary of the United Firefighters Union.

In Brisbane, where an estimated 4,000 people came together, firefighter Dean McNulty spoke of the huge concern climate change posed to his colleagues, who battle natural disasters from the front line.

Mr McNulty says scientists were clear that global warming would make extreme weather events more frequent and severe.

"To firefighters, it is not just numbers and statistics, it is very real," he said.

Rallies come as hottest year predicted

Global delegates in Warsaw for annual climate talks this week were warned by the World Meteorological Organization that 2013 was on track to be the hottest year since records began.

Australia's Bureau of Meteorology made the same prediction, and rally organisers encouraged people to wear "hot summer colours" to highlight concerns about extreme weather events.

The protests also targetted the Abbott Government's moves to repeal the carbon tax, after legislation was tabled in parliament last week to scrap the Labor-Greens initiative.

The two parties clashed after the Greens sided with the Coalition to fast-track an inquiry into the repeal bills, crushing Labor's chances of stalling a Senate vote for as long as possible.

The Greens have vowed to block the legislation, and leader Christine Milne said there would be more rallies if greater action was not taken.

"Tony Abbott wants to be defined by climate denialism, and the community wants to be defined by climate activism," she told media in Brisbane.

"This is really a showdown."

Ms Milne told the Brisbane rally that "Australians do not want our clean energy laws teared down".

Australia going backwards: Plibersek

In Sydney, deputy federal opposition leader Tanya Plibersek said the Government could not go backwards on climate change as global action galvanised.

"[While] Australia is going backwards, the rest of the world is going forwards accepting that climate change is real and accepting that we must act," she said.

Ms Plibersek criticised the Coalition for not sending a senior Government representative to this week's climate talks in Warsaw.

"Was a trading emissions scheme working? Yes. Electricity from old brown sources of energy down, renewable up by 30 per cent in the first year of its operation," she told the crowd.

"Australia can't go backwards in the face of global action."

At the Adelaide rally in Elder Park, chief executive of the Conservation Council, Tim Kelly, said recent events did not bode well for cutting carbon emissions.

"One of the most disturbing things has been the moves to wind back the carbon price, to abandon the clean energy finance corporation, to cut funding to the Australian renewable energy agency, and getting rid of the climate change authority," Mr Kelly said.

"We're really heading in the wrong direction to tackle climate change."

'Aim higher, we want climate action'

More than 500 people in Darwin marched from the Rapid Creek bridge to the Nightcliff pool in support of the event.

Chanting "Aim higher, we want climate action" and holding placards that read "Climate science is not a croc", the group demanded the Federal Government change its policy on climate change.

Stuart Blanch from the Northern Territory Environment Centre says a price on carbon is the best way to address climate change.

"We think they need to listen to the many people in big business who want a carbon price," Mr Blanch said.

The national director of GetUp!, Sam Mclean, says the rallies prove Australians believe climate change is a serious issue.

"From remote country towns to the big cities, Australians have come to their own conclusions after our hottest year on record. And they want action," he said.

A spokesman for GetUp! said Coalition MPs were invited to all the major rallies, but none responded.

The campaign has been strong on social media, with hundreds of people sharing photos and videos on Twitter, Instagram and Facebook.

ABC/AAP