Millions to swelter as new Sydney airport turns into summer 'heat sink'

In Western Sydney, oppressive heat is part of everyday life when summer rolls around, with temperatures in some suburbs regularly exceeding 40 degrees Celsius.

The sprawling 1,780 hectare Nancy Bird Walton Airport site is located in Badgerys Creek, a suburb that has previously recorded peaks of 50.1C on extreme heat days during summer.

Sebastian Pfautsch, a professor of urban planning at Western Sydney University who has spent years gathering data on the effects of urban heat, is concerned the region's new airport could act as a heat sink making nearby homes even hotter.

A heat sink is a term that refers to a localised area that absorbs lots of solar radiation and then re-radiates it making the environment around it warmer, he explained.

Nearby suburbs, like St Marys, have hit 48.9C, the same temperature that made Penrith the hottest place on Earth on a day in 2020.

Professor Pfautsch said the airport conditions could impede southerly winds for Penrith, which normally produce a cooling effect during extreme heat in the summer.

"Everything we know points towards the airport being a very large heat sink, so we have masses of unshaded black tarmac that, of course, acts like a local island that absorbs heat during the day and makes the air warmer," he said. 

"The cooling that naturally would occur from the south towards the north, so into Penrith, St Marys, Emu Plains, that area, that is now reduced because of hot air being produced around the airport and that's from the tarmac."

Summer temperatures in Western Sydney can be between 8C and 10C hotter compared to eastern and coastal areas, where there are sea breezes and higher annual rainfall.

A spokesperson for Western Sydney International Airport (WSI) said climate change risk assessments were carried out at every phase of the airport's design and construction.

"We mitigated every high and severe risk for climate change scenarios to 2090, implementing measures to protect airport operations from heat-related disruption," the spokesperson said. 

"This work was independently verified by the Infrastructure Sustainability Council and/or the Green Building Council of Australia."

'We're accelerating heat'

An abundance of dense concrete, lack of shade and housing with dark roofing in the region are additional driving factors for hotter conditions, as hard surfaces retain more heat than in spaces with vegetation.

Professor Pfautsch said a massive infrastructure project like WSI, in what already was historically the hottest part of Sydney, required offset measures.

"We're accelerating heat because of all the additional activity," he said of the 24/7 airport.

"There's lots of lots of dark surfaces that absorb heat, lots of additional car traffic, big trucks, lots of workers. All of that produces heat. Where are the offset measures for that?"

He said tree canopies and blue infrastructure such as lakes and canals or using reflective tarmac paint for runways could mitigate the urban heating effect of the new airport. 

"There's so much that we could do to actually inform how this whole airport aerotropolis area in central south-western Sydney could operate better during our hot summers," he said.

"We really need to do something for the people that still live there and work there."

How extreme heat could affect flights

ABC meteorologist Tom Saunders said the average mid-summer maximum temperature at WSI was about 30C, while Sydney Airport's mean maximum was 26.7C.

He said WSI could be up to 8C warmer than Sydney Airport depending on the wind direction and this summer was "looking particularly hot".

He said according to climatological data, days where temperatures exceed 40C typically arrive from December, and the region averaged about three days per year above 40C.

Jason Middleton from the School of Aviation at the University of New South Wales said hotter temperatures affected engine performance and made take-offs and landings more challenging. 

"The air becomes less dense at higher altitudes, and aircraft performance [both aerodynamic lift needed to take off, and engine thrust needed to take off] are lower in less dense air," he said.

Professor Middleton said thinner air density meant the landing distance and the take-off distance would be much longer than usual, although this was likely to impact larger aircraft.

For example, an Airbus A380 at maximum take-off weight would require a take-off distance far in excess of the available runway, if the temperature was over 35C and winds were light, he said. 

"Such a flight would need to reduce payload in order to make a safe take-off within the available runway."

He said he did not expect medium-passenger or smaller aircraft, like the A320 and Dash 8, to be affected by hot days at WSI but said he observed some instances extreme heat grounded the aircraft at airports in regional Queensland. 

"In Queensland, in the summer, they couldn't take everyone who was booked because it was so hot," he said. 

"The fuel and the weight of the passengers and their baggage, they were too heavy to get off on the limited runway length at the airports."

Professor Middleton said turbulence from crosswinds could also prove challenging for flights landing at WSI. 

"When you get very strong south-westerly winds, which you do typically get in August, you get west to south-westerly winds and they create turbulence and Western Sydney International Airport is basically in a position where it's susceptible to that."

He said days when turbulence is predicted to be severe "could be a real problem", as flights may be diverted to the heavily congested Sydney Airport.

"I can see potential problems happening down the road there where the overload from when [WSI] is not able to be used … the aircraft will have to go to Sydney Airport and Sydney will get bogged down."