We dont need name calling. But we do need to talk about climate change and bushfires.

The recipe for a bushfire is fairly simply in concept. One, take a spark, any spark it doesnt matter if its from a lightning strike, or a downed powerline, or a 10-year old with a box of matches. Two, add something to burn, like some nice dry leaves. And three, do this on a day which is preferably hot and windy, with low humidity.

Its logical that anything that increases the probability of ignition (1), the flammability of the fuel (2), or the conditions that promote fire spread on a particular day (3), will increase the risk that a fire will start, then spread.

Climate change is likely affecting all three ingredients of the recipe. Lightning ignitions are projected toincrease by about 12% with every degree of warming, although observations of this trend are scant thus far. But the relationship of the changing climate to the fuel and weather parts of the equation is very strong, and we are seeing the tragic effects being played out with unprecedented fire conditions currently affecting NSW, Queensland, and now Western Australia.

The dryness of ingredient two, the fuel, is a critical factor right now. Parts of northern New South Wales and southern Queensland are currently experiencing their driest conditions on record, with99% of New South Walesand66% of Queenslanddrought affected. The33 monthsfrom January 2017 to September 2019 have been the driest on record for the Murray-Darling Basin, particularly in the north, and for New South Wales as a whole.

Not only do these dry conditions mean that that the vegetation waiting for the spark is highly flammable, the lack of moisture in the soil means that air moving across the land is also extremely dry.

Then if we add in extreme conditions for ingredient three, the weather, the stage is set for disaster. Last Tuesday, the forecast 38oC temperatures, plus strong gusty winds, led to the very first declaration of Catastrophic fire conditions for Greater Sydney.

But really, none of this should come as a surprise. In Australia, the annual number of hot days (above 35C) and very hot days (above 40C)has increased substantiallyover most areas since the 1950s. Heatwaves are also lasting longer, reaching higher maximum temperatures and occurring more frequently over many regions of Australia.In 2019, NSW had its warmest January to August period on record for overall mean temperature (1.85C above average), and Australia as a whole had its warmest period on record for maximum (daytime) temperature (1.71C above average), and the second-warmest for average temperature (1.30C above average, behind 2016). Maximum temperatures on the 5thand 6thSeptember, were more than 10C above average in some areas.

Fire and emergency services use a handy tool called the Forest Fire Danger Index (FFDI) to forecast fire danger on a particular day. Developed by CSIRO scientist A.G McArthur in the 1960s, the index is a composite measure that incorporates temperature, wind speed and humidity, with a dryness record, based on previous rainfall and evaporation. When first developed, the index was on a scale of 0 to 100. Presumably, at that time, no one seriously considered a score close to 100. On Black Saturday, the FFDI was 155. On the 6thSeptember, in a place called Murrurundi Gap in Queensland, it was 174.

As the climate continues to warm and rainfall patterns continue to change, our bushfire seasons are lengthening not just by days or weeks, but by months! Longer bushfire seasons have many practical consequences. The window for performing safe hazard reduction is narrowing, resulting in more fuel build up close to residential areas. With bushfire seasons also lengthening in the Northern Hemisphere, our ability to share expensive resources like water-bombing aircraft and fire-fighting personnel is also becoming increasingly limited.

On Thursday14 November, the former head of NSW Fire and Rescue, Greg Mullins, stood in front of multiple TV cameras with four of his fellow former fire chiefs and spoke very bluntly. Heres an excerpt:

This fire season is going to go for months, so do we just simply get gagged?….Some people want the debate gagged because they dont have any answers. Its OK to say its arsonists fault, or that the greenies are stopping hazard reduction burning, which simply isnt true, but youre not allowed to talk about climate change. We are, because we know its happening.

Last April, Mullins and 22 fellow ex-fire and emergency chiefs formedEmergency Leaders for Climate Action (ELCA)and delivered ajoint statementcalling on the Prime Minister to meet with them. He didnt. They asked again in September, as it was becoming clear that unprecedented fire risk was upon us. He still didnt.

After all the publicity over the past week, ELCA has now been promised a meeting with the Minister for Natural Disaster and Emergency Management, David Littleproud. With four lives and nearly 350 homes lost, and over a million hectares burnt (and its still spring), many would suggest this isnt good enough.

When there is a bad road accident, politicians are quick to talk about the dangers of fatigue and speeding. When the Grenfell Tower fire killed 72 people in West London in 2017, the role of flammable aluminium cladding was front and centre. When there is yet another mass shooting in the US, the role of gun control (or rather the lack of it), is the first topic of conversation though the National Rifle Associations playbook echoes that of some of our own politicians over the past few days at a time like this, talking about the cause of a problem is insensitive and inappropriate. Instead, they offer thoughts and prayers. For the victims, whether from bushfires or any other tragedy, this isjust not enough.

There is no time like the present to talk about the risks posed by rapid climate change. If we dont talk about it, we dont acknowledge the problem is getting worse. And if we dont acknowledge this, we dont address the cause, or prepare adequately for the next crisis.

PM, lets talk.

Prof. Lesley Hughes**,** Pro Vice-Chancellor (Research Integrity and Development),Distinguished Professor of Biology