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The dreadful heatwaves that threaten our cities

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Parts of Victoria and NSW are sweating through an extreme heatwave that started sweeping across Australia’s southeast yesterday.

This may seem like just a good excuse to go to the beach, but as the planet warms and summers become longer and less bearable, heatwaves are coming to represent an existential threat to Australian suburbs.

Already, heat kills more people in Australia than any other natural disaster, including floods, cyclones and bushfires.

Now, faced with the prospect of 50-degree-plus summers, experts say highly urbanised parts of Australia may become unliveable within decades.

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The race is on to re-imagine, redesign and rebuild the Australian suburb.

Car parks may be ripped up and planted with trees and greenery, houses retro-fitted with insulation, roads painted to reflect rather than absorb heat, and supermarkets and even whole suburbs built underground to reduce cooling costs.

Children frolic in a fountain, but in the not too distant future staying cool any way we can will be a simple matter of survival. Photo: Getty

One centre of these efforts is Western Sydney, home to more than 2.5 million people.

In this floodplain of closely packed houses, heat pools on islands of black bitumen and collects on sun-baked concrete.

The mercury gets close to 50 degrees Celsius here in summer — and that’s just the ambient air temperature. The radiant heat from bitumen carparks can push 80C. The surface temperature of playground equipment has been measured at 100C.

Since 2019, all 33 Sydney councils have been funding a climate adaptation program that has identified heat as the number-one climate threat to Sydneysiders.

“We are not yet building a city that’s really equipping our people to survive and adapt extreme heat,” says Beck Dawson, who heads the Resilience Sydney program.

“If the community doesn’t have access to things to make themselves cool we effectively have a very large oven occurring across the Western Sydney plains.

“The scale of the emerging threat is different to anything we’ve faced before.”

When Penrith hit 48.9C

A taste of that future came on January 4, 2020, when Sydney — surrounded by bushfires — was struck by a heatwave that broke temperature records.

In the suburb of Penrith at the foot of the Blue Mountains, the mercury hit 48.9C, making it one of the hottest places in the world on that day.

At her nearby practice in Blacktown, GP Kim Loo prepared for the worst.

“It’s a sense of dread,” Dr Loo says about the days of forecast high temperatures.

“I have isolated patients who are near poverty or the working poor who are frightened about power prices.”

“I’ve got quite a lot of patients with heart failure, respiratory failure and little kids with asthma.”

In Sydney, the most expensive suburbs are also the coolest — the harbour and coastal areas are often 10C cooler than inland.

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Blanketed by smoke from ceaseless bushfires – as in this picture from last year’s Black Summer — and sweltering as the mercury soars, cities aren’t built to survive. Photo: Getty

The highest temperatures are usually recorded in low socio-economic areas with a high proportion of people who are vulnerable to heat, including the elderly, those who are socially isolated, and those on pensions who cannot afford to run the A/C.

“Air con is so important because [when temperatures rise] over 35C fans just don’t cut it, but running the air con is so expensive,” Dr Loo says.

“Many of my patients cannot afford it. I advise them to go to shopping centres.”

Baked in Blacktown

On a hot night in Blacktown, the 24-hour Kmart is a hub of social activity: people linger until it’s cool enough outside to go home to sleep.

The ad hoc reliance on shopping centres to keep cool illustrates the scale of Western Sydney’s emerging heat problem, says Ms Dawson.

“We’re putting one million more people into Western Sydney and they’re not all going to fit into Kmart on the fourth day of a heatwave,” she says.

But most of the really vulnerable people, she says, suffer through the really hot days in silence — they stay inside and keep the curtains drawn.

A project called Sweltering Cities is surveying residents to hear what it’s like to live, work and travel around Western Sydney on days of extreme heat.

The responses so far paint a scary picture, says Emma Bacon, who’s running the survey.

“The amount of people who use the word ‘dread’ with me about summer is shocking,” she says.

“Overwhelmingly, they’re saying political parties should have policies to address the heat in the city.”

The CSIRO and Bureau of Meteorology estimate the average number of days over 35C in Western Sydney could increase by up to five times by 2090. Put another way, Western Sydney will have an extra month of days over 35C by 2090.

Mattheos Santamouris, a professor at UNSW and a globally recognised expert on building cooler cities, believes that without action to help residents adapt to hotter summers, “many places” in Western Sydney will be abandoned over the next 20 to 30 years.

To understand why this may be the case, Professor Santamouris says it is first necessary to consider Western Sydney’s geography.

The desert to the east acts like an open oven door, blasting hot air at the suburban sprawl.

Sea breezes help cool the city, but only reach as far as the edge of Parramatta. Combined with climate change, high-density development and clearing of the tree canopy, the westernmost suburbs are getting alarmingly hot.

“If we don’t apply a very radical agenda for the next years, most people will move towards the coast where the sea breeze may help a lot,” Professor Santamouris says.

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Public life, he predicts, will shift to air-conditioned malls. He’s noticed this happening already in Darwin “where the main commercial street is not visited at all.”

An angry sun sinks in a shimmering haze during a recent Perth heatwave. Photo: ABC

Resilience Sydney’s Beck Dawson believes Western Sydney will remain habitable, but people will have to live there in very different ways to what they do now.

She suggests daily heat-risk rating system, similar to the one used for bushfires, could be introduced.

“When we get to extreme heat we have to respond as if it’s an emergency,” she says.

Dr Loo is less confident. From her medical practice at the frontline of climate change effects, she foresees a future of rapidly escalating health costs due to summer heat.

“With the number of hot days we have within Western Sydney — if we don’t have adequate adaptation — Western Sydney is not going to be liveable,” she says.

Thirsty trees

Action on heat takes two forms: mitigation and adaptation.
Mitigation is reducing the ambient air temperature itself (through planting trees or using heat-reflective materials), while adaptation aims to soften the impact of high temperatures (such as building houses with insulated roofs and double-glazed windows).

Trees lower temperatures, but only so far. Too much heat and their fate will be sealed. Photo: Treehugger.com

So far, NSW Government efforts to mitigate the extreme heat of future summers has focused on increasing the tree canopy across Greater Sydney by planting one million trees by 2022.

But though these programs are worthwhile, they are not enough on their own to counter the rising heat, says Professor Santamouris, who calculates that planting five million trees would only decrease the maximum temperature in Western Sydney by 1 to 1.2 degrees.

In some scenarios, he said, trees can even make the city hotter.

Once trees get too dry, they draw water from their leaves into their trunks, so that they no longer have a cooling effect on air temperature. This can be countered with irrigation, but millions of trees would require a lot of water.

“Just planting a number of trees will not solve the problem,” Professor Santamouris says. “We need to have much more radical solutions.”

Lost in space

One simple solution is to use more light-coloured building materials that reflect rather than absorb heat. Trials have shown that painting road surfaces with heat-reflective paint can keep them at least 10C cooler than untreated sections.

Widespread use of these cool materials could reduce the ambient air temperature in Western Sydney by 1.5C, Professor Santamouris calculates. Next-generation “super-cool” materials could double that figure.

Berlin’s Aldershof Photonics centre demonstrates how science can foil the impact of soaring temperatures. Photo: Artur Hassa

These materials, called photonics, radiate heat at a frequency of infrared that, rather than being absorbed by the atmosphere and bouncing back, sends the heat into space. They can be applied as paint or a spray-film for plastics and even wood to stay up to 10C cooler than the ambient temperature.

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“We expect them to be ready in the next few years,” Professor Santamouris says.

But even these high-tech materials are no match for the impact of climate change, he says.

The reduction in temperature through mitigation will be mostly cancelled out by the projected increase in ambient temperature. “Given that, mitigation is not enough,” Professor Santamouris says.

Refuge bunkers

That leaves adaptation: reducing the impact of the heat.
Sebastian Pfautsch, an urban heat expert at Western Sydney University, proposes replacing the model of runaway suburban sprawl with one that prioritises green space.

He’s calculated that in some Western Sydney’s suburbs, 80 per cent of the surface area is sealed with roads, pavements, car parks buildings and other kinds of construction that trap heat. That figure, he says, needs to get down to 25 per cent.

“If you don’t want to have urban development where you increase the temperature then you can only achieve that where you’re the covering area with two portions open space and one portion of closed space,” he says.

To do this, he says, houses and shops need to be built largely underground, which has the added advantage of making them easier to cool.

Along with escaping the dreadful heat by going underground, scientists also envision integrated high-rise eco towers. Photo: WebUrbanist

Another option is to house people in high apartment blocks surrounded by vast areas of parkland.

“We need to build up or build down,” he says.

“This may sound utopian but it is a necessary type of progressive thinking in hot areas. “A large shopping centre built underground can bring its cooling cost down by 95 per cent.”

Other ideas include retro-fitting homes with insulation and air-conditioners as well as providing cheap renewable energy.

Renters or people without access to suitable roof space could purchase or lease solar panels in a centralised array, with the electricity generated credited to the customer’s electricity bill.

Such “solar gardens” are already operating in regional NSW, with customers in Western Sydney.

Then there are plans to better forecast and track heat.

Several Western Sydney councils have commissioned Dr Pfautsch to install thousands of temperature readers to map the eddies and flows of heat in their area.

The Bureau of Meteorology has introduced a national three-day heatwave forecast and is also working on a “heatwave predictability map” that it hopes will better inform Australians about the severity and duration of each heatwave as it rolls in.

ABC

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