In early 2019, Mullins, who lives in Cromer on Sydney's Northern Beaches, along with 22 other former emergency service chiefs, tried to warn federal and state governments that a dangerous summer of bushfires was looming. They also called for a meeting with the prime minister to discuss the escalating climate change risks.

Later that year, as the state plummeted into what's now known as Black Summer, the chiefs were attacked by some sections of the media, by an outspoken media personality and by politicians who said the fire emergency was not the time to discuss climate change.

His debut book Firestorm calls for action on climate change, and he told ACM why it had become political.

"I'm frightened because the sorts of changes I've seen in weather and the ferocity of fires and how much damage they're doing shouldn't have been possible during my lifetime. In a natural progression, maybe centuries, but it's centuries of change squashed into 50 years.

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"There's one study that really frightens me actually. It says on the current trajectory of emissions, by 2040 the summer of 2019 - which was the hottest, driest ever recorded in Australia - will be average. Black Summer will be an average fire season. By 2060 it will be exceptionally cool, they're talking about heatwaves reaching 60 degrees and I don't know how you fight fires in it, we tried to fight fires in almost 50 degree heat and you couldn't do it.

"We must stop that from happening, and we can.

"[The public attacks] were very personal and that's what they do. Unfortunately the coalition, if they don't like what people are saying, they go on a personal attack.

"It is a political problem. A lot of people aren't happy with the major political parties because they're locked in this climate war and it's almost a race to the bottom, to who can do the least. Maybe we need independent candidates in hung parliaments who can influence the government?

"It's vested interests and people are frightened, it's too big a problem to digest. Look at the Great Barrier Reef, we've lost half the barrier reef and people are in denial, so if we can put it off for someone else to deal with, hallelujah

"It's got to the stage now where we are the generation who must deal with it.

"The CSIRO and Bureau of Meteorology say the temperature's gone up by 1.4 degrees since 1910. Just that tiny little change in temperature has changed weather systems so we're getting more extreme weather, our bushfire seasons are getting longer, so instead of starting in October each year, which they did for basically 200 years in NSW, they're often staring in August.

"Fires can burn for months, the Gospers Mountain fire [which burnt for 79 days during Black Summer] ended up the biggest forest fire ever recorded in Australia. It was over a million hectares eventually and it swallowed up three other fires.

"The scientists are saying it and the royal commission's saying that because of the emissions already in the atmosphere, it's going to continue to warm until mid-century, no matter what we do. Fires will get worse, cyclones will get worse, the heatwaves and the droughts.

"What happens after that is going to be entirely based on what we do now about emissions. If we drastically cut them we can stabilise by mid-century and eventually drive it down and if we don't it'll just continue to get worse.

"I've got grandkids and I have a moral duty to do anything I can to get the facts out there, there's so many lies and so much misinformation and I just couldn't sit back.

"I think it was a story that needed to be told. It's all there - the mythbusting, like 'it was the rotten greenies', 'it was national parks not doing their job', 'lets graze our cattle in the national parks that'll do it', 'the 1851 fires were worse'. All these myths I deal with in there and say none of that stuff is true.

"I do all I can putting out fires on fire trucks but I'm probably more effective writing a book and speaking to the media and getting true information out there.

"I'd love to just sit back and put my feet up and I don't like getting attacked personally by politicians and some media personalities for stating facts, but if that's part of the territory so be it."