Tens of thousands of Australians gathered in more than 100 places across the country on Sunday to demonstrate their support for greater actions on climate change.

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

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

At the rallies across the country, emergency workers played a significant role in warning of the dangers of unchecked global warming, while Labor and Greens politicians, along with climate scientists, also participated.

In Canberra, organizers estimated that up to 2,000 people attended the event in Canberra CBD.

David Livingstone, ACT secretary of the United Fire Fighters Union, told the crowd that more frequent bushfires were putting the lives of his members at risk.

"We have seen more major bushfire events in our lifetimes than our grandparents did in theirs," Livingstone said."That's climate change and we need to do something about it."

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.

McNulty said scientists made 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," the Australian Associated Press (AAP) quoted the United Firefighters Union (UFU) representative as saying.

In Melbourne, where some 30,000 people attended the gathering, Greens deputy leader Adam Bandt evoked the memory of the 2009 Black Saturday bushfires. During the series of bushfires on February 7, 2009 in the state of Victoria, 173 people died, making it the the highest wildfire casualties in Australian history.

In Sydney, about 3,000 protesters rallied in the city's Prince Alfred Park to call for stronger action on climate change from the government.

"Today is a challenging period in our political history. It's a time when our government is sacrificing our planet for politics," GetUp campaigns director Erin McCallum told the crowd.

Deputy federal opposition leader Tanya Plibersek said the government needed to get back to basics on climate change.

"Australia is going backwards, the rest of the world is going forwards accepting that climate change is real and accepting that we must act," Plibersek told the crowd.

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 said a price on carbon is the best way to address climate change.

The newly-elected Liberal-National government is pushing in the Parliament for laws to repeal the carbon tax, introduced by the previous Labor government on July 1, 2012.

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