A group of 33 former fire and emergency services chiefs wants the royal commission to record as fact that climate change was the main driver of the extreme weather conditions behind Australia's unprecedented bushfire season.

"We think that this is a great opportunity for an authoritative body to spell out loud and clear that if it wasn't for climate change we would not have faced the bushfires that we did," former Fire and Rescue NSW commissioner Greg Mullins told AAP.

"That the science is very clear that we would not have had weather conditions like we did if it wasn't for a warming climate and the fires were driven by extreme weather."

The Royal Commission into National Natural Disaster Arrangements starts hearings in Canberra on Monday with a focus on the changing global climate and natural disaster risk.

The Emergency Leaders for Climate Action group said the evidence was irrefutable that climate change caused by the burning of coal, oil and gas "super-charged" the 2019-20 bushfire season.

"It is not possible to 'adapt' to such catastrophic conditions and they can only be partially mitigated," its submission to the inquiry said.

ELCA warned Australia inevitably faced escalating and catastrophic natural disasters in the future because of past emissions, calling on the federal government to urgently act.

"In so doing (it would) provide future generations with some prospect of withstanding or avoiding what is currently a nightmare scenario of natural disasters whose consequences will be of such a scale that they will not be able to be effectively mitigated against, adapted to or responded to."

ELCA also argued Australia urgently needs to adopt new methods to detect and rapidly respond to bushfires as quickly as possible and stop them developing into mega-fires.

"We need to jump on these fires immediately," Mr Mullins said.

Mr Mullins said Australia needed more fire-fighting aircraft, specifically smaller, more flexible water-scooping aircraft used in Europe, Canada and on the US west coast.

"You'll drop far more water and foam on the fires than you ever will with the big aircraft that have such long turnaround times," he said.

The 'Black Summer' bushfires killed 33 people, destroyed more than 3000 homes and burnt about 12 million hectares across Australia.

In addition to climate change, the royal commission's two-week hearing will focus on the impact of the 2019-20 bushfires and the Commonwealth's responsibilities when it comes to natural disaster arrangements.

The first witnesses on Monday will be scientists talking about climate trends and key drivers of natural hazards such as bushfires, cyclones and floods.

Australian Associated Press