Urban heat islands
Last week, Scientia Professor Mattheos Santamouris, presented a lecture entitled “Cooling Our Cities — advances in science and design for the mitigation of urban heat”. This is a focus subject for our group project.
Professor Santamouris covered a great deal of material, and offered many graphical accounts from papers such as Analyzing the heat island magnitude and characteristics in one hundred Asian and Australian cities and regions — one that I had downloaded for our group project but had not yet had the chance to read.
I will list the key points from the lecture here and then briefly discuss some reflections:
- The thermal balance of the urban environment differs substantially from rural areas and is increasing at a greater rate than that of the planet.
- The duration of hot spells in Australian cities is increasing, meaning fewer opportunities for cities to cool down.
- Two synoptic systems define the temperature of Sydney: the cool sea breeze and warm wind from the desert.
- There is significant impact on peak power demand in Sydney because of heat. People in the west need to cool their houses twice as much people in the east during hot weather.
- Low income households are affected both by hotter thermal temperatures in their houses, and increased indoor pollution because of this heat.
- The impact on health and mortality from heat will be significant in the future. A predicted 275% increase in deaths because of heat.
- Although technologies are being developed to help us adapt to increased heat from climate change, Professor Santamouris suggests that mitigation strategies are just as important.
- The layout of cities can assist in reducing the impacts of heat. The impact is dependent on the height of buildings and the width of streets.
In readings for Week One I was struck by the case study of the German city of Munich and how they radically altered the layout of the city to allow for cool air to reach the city during warm days. It is “an unusually direct application of climate analysis to urban design” (Hebbert, M. & Jankovic, V. 2013). As Professor Santamouris mentioned the cool breezes from the east in Sydney and the hot wind from the west, I wondered if in Sydney we would be brave enough to enact such radical urban design. I fear not.
Instead, development occurs at pace, without concern for rising heat. Just this evening on ABC News a report looked at the increased development in the south west of Sydney around Camden. No mention of heat impacts, just the problems residents fear from overcrowding. All of the images shown on the program were of houses with black roofs—which seems more of an issue given the rising heat in our suburbs. Studies have shown that on day where temperatures reached 33 °C, black roofs reached 68 °C. This compares to white roofs which measured 42 °C and green roofs which were between 31 °C and 38 °C (Santamouris, 2014).
REFERENCES
Hebbert, M. & Jankovic, V. 2013, “Cities and Climate Change: The precedents and why they matter”, Urban Studies, vol. 50, no. 7, pp. 1332–1347.
Santamouris, M. 2014, “Cooling the cities — A review of reflective and green roof mitigation technologies to fight heat island and improve comfort in urban environments”, Solar Energy, vol. 103, pp. 682–703.
