The former Australian of the Year has told a Sydney conference the world is in for a difficult couple of decades, even under the most optimistic climate action scenarios.

The greenhouse gases humanity has already produced will continue to warm the planet for years to come, meaning the calamities Australians have recently endured will be dwarfed by what's coming.

"The extremes that we do experience a decade from now will be way outside of anything that we will have seen to this point," Prof Flannery told the International Congress of Actuaries on Monday.

"Even if we cut emissions as hard and fast as we possibly can things will continue to deteriorate for a decade or two and unfortunately we are in danger of reaching tipping points in the climate system."

He said there were lessons for Australia in how it dealt with the early stages of the COVID-19 pandemic.

"The first thing the government did was stop the problem getting any bigger. That meant stopping flights from China, which was then the source of the infections.

"It meant paying a very significant economic cost to keep people home, and of course restricting personal liberties. We did all of that in the hope that we as a society, as a whole, would benefit."

The government also invested heavily in the health system, making sure it could adequately respond and the same style of approach was needed for the climate crisis, Prof Flannery said.

"We need to create a sufficient emergency room for all of the consequences of warming," he said.

"When you are dealing with climate change, the emergency room has to be dealing with adaptation, with our coasts, with how we protect our most vital infrastructure, and how we have an orderly withdrawal from areas we can't defend."

He said health and emergency services must be properly resourced to cope with future heatwaves, fires and floods while work continued on a "vaccine" - a clean energy system and new tech to suck existing greenhouses gases out of the atmosphere.

"I'm sorry to say it's going to get worse for a little while - almost regardless of what we do," said Prof Flannery, who led the Climate Commission before the Abbott government axed it a decade ago.

Since then he's served as the chief councillor of the Climate Council, which rose from the ashes of that termination.

Prof Flannery told delegates the world sailed passed an opportunity for a "relatively simple and inexpensive" transition away from fossil fuels in 2009, when the Copenhagen summit failed to set basic targets to cut emissions.

"And in the 15 years or so since ... humanity has released around a third of all of the greenhouse gases that we have ever emitted. That is a very, very large increase in a very, very short time and it will have consequences."

Australian Associated Press