The former head of NSW's urban fire service says early Australian bushfire seasons are here to stay - and the federal government must step in as resources and firefighting assets stretch beyond current capacity.
Greg Mullins served as commissioner of Fire and Rescue NSW from 2004 until his retirement in 2017 and currently sits on the Climate Council, a national climate change communications body.
With NSW bushfires making an early mark in 2019 - including the destruction of nine homes over the past week in the state's north - Mr Mullins told AAP authorities should prepare for more of the same in coming years.
He said the entire Australian strategy of tackling bushfires - sharing firefighting resources between states as the risk moves from northern states in spring to southern states in summer - was under threat.
Climate change has made nights and winters warmer, increasing the possibility extreme bushfires would burn in different states simultaneously.
"What's becoming difficult is the whole paradigm of strategic firefighting in Australia - it was predicated on progressive fire seasons," Mr Mullins said.
"As we saw last year and now, we're getting simultaneous fire seasons.
"States are having to resource their own fires while other states are screaming out for help and there'll be times when each state says, you're on your own."
Australia currently leases six large firefighting aircraft from the northern hemisphere each summer, and NSW has purchased one 737 Large Air Tanker.
Mr Mullins said that, with the effects of climate change set to intensify over the coming decades, the government would be obliged to buy more aircraft.
"There's a cost to this, to adapt to a new and more dangerous present ... we need lots and lots of large firefighting aircraft," Mr Mullins said.
About 50 bushfires continue to burn across NSW.
Mr Mullins was one of 23 former Australian fire and emergency chiefs who in April issued a joint letter to Prime Minister Scott Morrison, calling for the country to take greater action against greenhouse gas emissions.
The group also warned of burnout among emergency service volunteers.
Former NSW Fire Brigade deputy commissioner Ken Thompson on Thursday predicted the coming fire season would be the worst in Australian history.
Federal Natural Disaster Minister David Littleproud this week said drought had "exacerbated" fires across the country but refused to be drawn on whether human-induced climate change was to blame.