2 March 2018

'Heat Islands' stop Canberra from cooling down according to CSIRO report

| Lachlan Roberts
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Climate change

A CSIRO report commissioned by the ACT government has found that temperatures in many urban areas are warmer than their rural surroundings, with Canberra suburbs and neighbourhoods the hottest.

Canberra suburbs are hotter due to the ‘urban heat island effect’, which is when pavements, roads and buildings absorb the sun’s heat and radiate it back day and night, increasing the temperature.

The heat islands are stopping Canberra from cooling down, and the Minister for Climate Change and Sustainability, Shane Rattenbury, is calling for a plan to manage the city’s heat.

Mr Rattenbury believes that Canberra’s heat will become a greater problem as climate change causes warmer weather and more extreme temperatures.

“This report shows that we need to plan, build and manage our city in a way that meets these challenges,” Mr Rattenbury said.

The CSIRO report found that Canberra’s summer land surface temperatures can be up to 100 C hotter by mid-morning in parts of the city, and up to 80 C hotter than surrounding rural areas at night.

Areas with large surfaces such as rooftops, carparks and paving, commonly found in commercial and industrial areas, major roads and intersections, and new housing developments typically experience above-average temperatures on summer mornings.

According to the report, neighbourhoods with tree canopy shade of 30 per cent or more can be up to 130 C cooler on a hot summer day, with Canberra’s most vulnerable groups – low-income households and the elderly – more at risk in extreme heat conditions.

Mr Rattenbury believes that more water bodies and shade trees will reduce land surface temperatures.

“One option to reduce land surface temperatures is more living infrastructure – for example, wetlands and water bodies, parks with watered grass, shade trees, and buildings that incorporate greenery on their walls and roofs,” Mr Rattenbury said. “Living infrastructure and energy efficiency is increasingly becoming part of our way of life.”

He said urban densification presented a challenge, but with those redevelopments planners need to make sure they’ve got the green walls, green roofs, and that there was space left to plant trees around them.

“You can have urban densification and a good urban cooling strategy, you just need to be very deliberate about it, and so for me this report really sets the challenge for building designers, town planners and government agencies to make sure we have the requirements in place, and not just build concrete monoliths,” Mr Rattenbury said.

“There are great examples around where buildings aren’t just all concrete, where there are courtyards inside buildings that are well planned that have got green lawns.”

Mr Rattenbury said the tree species used in the living infrastructure would change with the the climate.

He said Transport and City Services, which is responsible for the urban forest, was already looking at adapting the species used in Canberra as the city gets hotter and dryer.

“Some trees that we’ve planted in the past will no longer be suitable for Canberra and we’ll need to use different species,” he said.

Mr Rattenbury said that a living infrastructure plan will form part of the new climate change strategy, the ACT’s Climate Strategy to a Net Zero Emissions Territory.

Canberrans are encouraged to take part in the development of the strategy, which is open for consultation until 9 April 2018.

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More people die of cold related illness than overheating.

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