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Heatwaves and global warming

Victorian bushfire

It’s common knowledge that one of the main effects of global warming is an increase in the number and severity of extreme weather events.

That means more hot days, and hotter hot days. What that also means is a large, and growing, risk of bushfires. South-eastern Australia is one of the most fire-prone parts of the world, and rarely does a summer go by without reports of a major blaze, spurred by 40°C-plus temperatures and scorching northerly winds threatening the ever-expanding suburbs of Melbourne, Canberra and Adelaide, and occasionally even Sydney’s west.

Right now, Australia is in the grip of its second major heatwave for 2014. Fires have been raging in Victoria, in outer suburbs including Kilmore, Wallan, Warrandyte, Hazelwood and Gisborne. Residents of what are normally considered leafy enclaves are receiving emergency text messages telling them to prepare to evacuate.

As we spread further across the land, a heating planet is going to make this kind of bushfire weather more and more prominent. More people meeting more fires is never a good thing. Whether all this means greater bushfire and heatwave risk in the short term is in the hands of mother nature, but it’s time that the conversation about climate change and the escalating threat of bushfires (and heatwaves, cyclones, and floods) took place.

What we are seeing, here and around the world, is weather on steroids. Weather that is being super-charged by global warming. No one will ever be able to point to any given bushfire on any given hot day, and say “that’s climate change right there.” That’s not how this works. Rather, we can point to all future extreme hot days and bushfires and say “they are more likely as a result of a planet that is ever-hotter".

What we are seeing, here and around the world, is weather on steroids. Weather that is being super-charged by global warming

Imagine a six-sided die. That is Australia’s climate. On any summer’s day, the die is rolled to determine the day’s weather. A one is a cool, beautiful, mid-20s day with gentle breezes, while a six is over 40°C and threatening to start fires across south-east Australia. Climate change messes with the numbers. The longer global warming is allowed to continue, the more we’ll see sixes replace fives, and fives replace fours. It’s not inconceivable that this metaphorical die one day could have two sixes, two fives and four and a three.

The CSIRO has found Australian annual average daily maximum temperatures have steadily increased in the last hundred years, with most of the warming trend occurring since 1970. There has been an increase in the number of hot days and a decrease in the number of cold days. The Climate Council's recent report found that 2013 was Australia's hottest year on record and the nine preceding that have all come since 1990.

This hot-dry trend is expected to continue, with the Climate Council predicting large increases in the number of days over 35°C this century.

Victoria, in particular, has always been one of the world’s most at-risk areas when it comes to bushfires. According to the Climate Council, Melbourne is facing the prospect of twenty-seven 35°C+ days by 2100, up from nine today. What could this mean for bushfire risk?

We know that as global warming continues, each of those events was made more likely, and more likely to be bad, because we are living on an ever-hotter planet

The Climate Council's report on the link between bushfires and climate change shows that the frequency and intensity of bushfires is expected to increase substantially in coming decades in many regions, especially in those regions currently most affected by bushfires, and where a substantial proportion of the Australian population lives. Extreme fire danger days are expected to rise more than 15 per cent in south-eastern Australia.

Fire is fundamental to the nature of Australia. Our plants, animals and landscapes have been shaped by fire. Indeed, the very survival of many species and the health of entire ecosystems depend on fire. Indigenous Australians have used fire for millennia to improve hunting, for shoot growth promotion, fruit production and the protection of sacred sites.

Different types of bushland respond differently to different patterns of fire frequency and intensity. There is no ‘one size fits all’ approach to fire management. While we cannot completely control fire we can learn to manage it in ways that protect people and maintain healthy ecosystems.

The devastating Victorian bushfires of February 2009 claimed 173 lives. These fires started on a day of unprecedented fire danger that followed a fortnight of record-breaking temperatures and the longest drought on record. In addition to those killed in the bushfires, at least 200 people are believed to have died in Victoria as a result of the preceding heatwave.

This hot-dry trend is expected to continue, with predicted large increases in the number of days over 35°C this century

Climate change is leading to weather on steroids. We will never be able to point to a bushfire, or a cyclone, or a flood and categorically say ‘climate change caused this’. But we know that as global warming continues, each of those events was made more likely, and more likely to be bad, because we are living on an ever-hotter planet.

To avoid a repeat of the kinds of devastating bushfires we saw in 2009, all levels of government need to take urgent action to tackle climate change. Scientists continue to warn that it will bring hotter and drier weather in south-eastern Australia, together with more extreme heatwaves and heightened fire danger.