The heat island effect can basically be defined as the extra temperature that occurs in a place as a result of structures – roads, buildings, car parks – that retain heat compared with the countryside around it. You only need to put your hand on a brick wall or walk barefoot on a road at the end of a sunny summers’ day to recognise this. That is why the Bureau of Meteorology is particular about the siting of weather stations so that their measurements are not exaggerated by this effect. Their care in doing so has meant they have occasionally been criticised for adjusting the records of some weather stations to allow for this – usually by climate change deniers.
Anyone can calculate the heat island effect merely by measuring the minimum and maximum temperatures at your home and then comparing them with the equivalent amounts recorded at your local weather station. The difference between them is the heat island effect. In Bairnsdale the weather station is at the airport – about 5 kilometers from the CBD – and amongst the number of reasons for the choice of this site must also include the elimination of the heat island effect. I have measured this on several occasions. My observations indicate that at our location in town on hot days is from 1-2 degrees warmer than the measurements at the weather station. The effect is most noticeable with extreme temperatures including cold days like the record frost last year when a warmer town was most evident.
Climate change is influencing heatwaves, defined by the Bureau of Meteorology as “by three or more days of unusually high maximum and minimum temperatures in any area” making them more frequent and more severe. The extra degree of two of the heat island effect is on top of these temperatures. As the nights get warmer the overnight minimums after a run of hot summer days hovers in the mid to high 20s. This makes it very hard for our bodies to recover from the previous heat without artificial cooling.
The heat island effect and the extreme heat of climate change enhanced heatwaves can be lessened in a number of ways including by increasing greenery and shade in a town – especially trees. I have recently commented on the fact that Bairnsdale is a tree friendly town but much more can be done on this here and other towns in Gippsland.
Another way of reducing the heat island effect is by using reflective paint on dark surfaces. A white roof, for example reflects more than 90% of the energy that hits it back into space. Whilst cooler in summer the downside is that it is also cooler in winter. I have had the roofs of my last two residences painted with light reflective colours – in one case white and in our current unit a much less reflective cream. Applying light colours to some surfaces such as roads may cause problems with users being affected by summer glare. Rather than painting or surfacing car parks with a light coloured material perhaps they should have cover them – preferably with solar cells.
Other options include roof gardens or completely covering roofs with photovoltaics – now legally required on all new buildings in Paris. Similar actions are being adopted around the globe. All told local councils have it in their power to reduce the extreme temperatures in their cities and any effort in this regard (possibly as simple as changing a by-law or two) is a step in the right direction.