MICHAEL MCCORMACK, DEPUTY PRIME MINISTER: We want to put this above politics.

They don't need the ravings of some pure enlightened and woke capital city greenies.

CAROL SPARKS, MAYOR, GLEN INNES SEVERN COUNCIL: All the dams and creeks and rivers are dry and we need to look at what we're going to do about that in the future.

GLADYS BEREJIKLIAN, NSW PREMIER: I certainly don't think it's appropriate to get into a political argument as to what the causes are at this stage.

PAUL FARRELL, REPORTER: Bushfires have always been one of the most hazardous forms of natural disaster.

But as fire spreads across New South Wales and Queensland, debate has shifted to what is making our seasons more severe.

SHANE FITZSIMMONS, NSW RFS COMMISSIONER: In catastrophic circumstances, routinely, you can expect the most extraordinary of fire behaviour.

PAUL FARRELL: The fires across northern New South Wales this weekend have so far burned more than 850,000 hectares.

To put the size of this fire alone into perspective, the devastating Black Saturday fires in Victoria in 2009 were about half that size, burning around 430,000 hectares.

MARK HOWDEN, CLIMATE CHANGE INSTITUTE: What seems to have happened is that those bushfire seasons have extended.

So they're starting earlier, finishing later and so, the traditional idea of a bushfire season probably seems to have gone out the window in Australia, as it has in other places like California.

PAUL FARRELL: And it's not just a one-off event.

An analysis of fire warning data has also revealed that between 1973 and 2010 bushfire conditions have worsened in these locations across Australia.

MARK HOWDEN: A key driver is temperature but at the same time, we're seeing a really significant drought here, which also dries out that fuel and it also dries out the wind and so we're getting very dry wind coming across dry fuel, and that's a prime situation for fires.

PAUL FARRELL: The topic that has generated the most controversy is discussion around the link between climate change and bushfire intensity.

According to the CSIRO, Australia's climate has warmed by just over one degree since 1910.

MARK HOWDEN: One degree might not sound like much, but one degree makes a huge difference when you're thinking about the Earth's system.

PAUL FARRELL: A joint report by the Bureau of Meteorology and CSIRO found that climate change is contributing to a longer fire season.

GREG MULLINS, FORMER FIRE COMMISSIONER: We're coming into what I think is the most dangerous fire season, dangerous build-up to a fire season I've seen since 1994.

PAUL FARRELL: Last week on 7.30, former fire chief Greg Mullins had a stark warning that already appears to be coming to pass.

GREG MULLINS: Climate change is real, it's making it a more dangerous planet for everybody, but particularly in Australia.

It is going to be harder and harder to fight these fires and we need a national response to this.

MARK HOWDEN: So what we've seeing is an increased number of fires, increased severity of those fires, increased area burnt as well as increased fire season.

And they are all of the sorts of things we anticipate under climate change and unfortunately, the projections are for those to get worse.