12 May Urban Heat Islands (UHIs)-the lesser known part of the climate change puzzle
In my previous blogs, I have discussed a number of issues associated with climate change, including the issues faced by a number of Governments, the actions/policies they propose in the lead up to Paris in December and the latest news in the renewable energy/cleantech space around the world.
To date I have been remiss in not discussing one of the perhaps lesser known (but equally as important factors) that is increasingly being linked to climate change, and that is the concept of urban heat islands (UHIs). Urban heat islands are essentially small areas (or islands as the name suggests) where the annual mean temperature can be up to 3°C warmer than the surroundings as a result of the sun heating buildings, roads or footpaths (and for that matter any surface other than the natural landscape). In reality, two heat islands are created-one on the surface (eg. building, road or footpath) and one in the atmosphere around those surfaces. Surface heat islands will be more pronounced during the day when the sun is shining, and atmospheric heat islands will be more pronounced after sunset when the surfaces that have been heated during the day (and have stored all of that heat) slowly release it.
You may ask what this has to do with you? Well, if you are amongst the half of the world’s population that live in urban areas (and with the rate of urbanisation expected to increase by 70% by 2030), there is an increasingly higher chance that you will experience this effect, particularly as urban areas typically have busy roads or highway/freeways close to them. Unlike vegetation which grabs the incoming radiation from the sun and uses most of it in evapotranspiration, releasing water vapour and providing shade as it grows (both of which cool the air nearby), constructed surfaces (eg. buildings, roads, footpaths) comprise materials that are predominantly non-reflective and water resistant. Therefore, they will absorb the incoming radiation from the sun and later release it as heat.
In a series of blogs I will discuss in more detail why it is important to recognise what UHIs are, what their impacts are (eg. air quality) and the role they will increasingly play in the layout/design and construction of new city/urban areas. Given that Governments at State, Local and Provincial levels in many developing and developed countries alike are grappling with the issue of having to accommodate higher numbers of people living and working in increasingly larger and more dense city/urban areas, the management of UHIs is going to become more important going forward.