(AU SMH) UN’s ‘Code Red’ Climate Warning A Burning Issue For Australia’s Fire Risk

Sydney Morning Herald - Mike Foley

A landmark United Nations climate report mapped out with unprecedented certainty the nature of the dangerous bushfire future which will confront this country, according to the two Australian lead authors who were among the 234 contributing scientists.

Global warming will intensify the decline of southern Australia’s crucial winter rainfall and increase the number of extremes heat events. This combination will drive greater risks of extreme fire with more hot, dry, windy weather said Australian National University Climate Change Institute Professor Mark Howden.

Fires sweeps through the Snowy Mountains region in January 2020. Credit: Alex Ellinghausen

“The conditions that generate fire weather are likely to increase in both frequency and intensity,” Professor Howden said.

The Intergovernmental Panel on Climate Change, released last week, showed with greater confidence than ever before that the world is “very unlikely to avoid 1.5 or 2 degrees of warming under the current trajectory of greenhouse emissions”, Professor Howden said.

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UN Secretary-General Antonio Guterres said the report was “a code red for humanity”. While the world has on average warmed by 1.1 degrees due to human-induced climate change, Australia’s landmass has heated by 1.4 degrees due to regional weather conditions affecting the continent.

It was “increasingly clear climate change has played a significant role in extreme heat events in many regions” such as Australia’s 2019/20 Black Summer bushfires, a heat dome in the United States and the fires burning in southern Europe, Professor Howden said.

A joint study by the Bureau of Meteorology and CSIRO found southern Australia had already lost significant seasonal rainfall. Winter rainfall has reduced by 11 per cent in the south-east, and winter rainfall is down 20 per cent in south-west Western Australia since 1970, compared to the previous 70 years.

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While summers with above-average rainfall will become more likely because for each degree increase in air temperature the atmosphere can hold seven per cent more moisture, extra rain won’t wet the landscape and reduce fire risk, Professor Howden said.

Winter rain in southern Australia evaporates less than in summer, which soaks into the soil and stays in the landscape for longer to reduce aridity when hotter weather hits, he said.

“We’re losing our useful rainfall (in winter) and gaining not very helpful rainfall in summer. That summer rainfall is inherently very variable and it’s not particularly useful in terms of changing the moisture profile in the landscape because most of what rain does fall evaporates fairly quickly in summer,” Professor Howden said.

“Those wetter years generate large amounts of fuel and then in the dry years, that will form as (forest) litter, and it will become extremely dry and very flammable, so that variability can actually drive the in predisposing factors for really big fires.”

With the world tracking for 2 degrees of warming or more, the other Australian IPCC lead author, Professor of Climate Change, Roshanka Ranasinghe, said in that scenario there are dozens of what’s known as climate impact drivers that will play out.

Professor Ranasinghe, from the IHE Delft Institute for Water Education, said “we have high confidence that 11″ of those scenarios will hit Australia such as rising temperatures and extreme heat.

Meanwhile, a study by CSIRO and Bushfire Co-operative Research Centre has found a uniquely dangerous weather system that spews hot, dry air from the interior across eastern Australia like a fire hose could occur up to four times more often by 2100 if greenhouse emissions continue unchecked.

The system occurs when a low-pressure system races northwards from the Southern Ocean and collides with a high-pressure system on the NSW coast. The two systems rotate around each other and suck hot, dry air from inland Australia out towards the coast, resulting in high and dry westerly winds that can run for days.

Links

• Storms, tornadoes and explosions: How bushfires are getting stranger
• ‘Still in the control cabin’: Time running out to limit warming, IPCC says
• Australia's changing climate
• Experts warn extreme bushfire weather risk growing
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