What is an Urban Heat Island (UHI)? From http://en.wikipedia.org/wiki/Urban_heat_island: An UHI is a metropolitan area that is significantly warmer than its surrounding rural areas due to human activities. What causes it? To put it simply, these are what Wikipedia lists as causes:
- Waste heat from automobiles, air conditioning, industry, and other sources.
- High levels of pollution in urban areas can also increase the UHI, as many forms of pollution change the radiative properties of the atmosphere.
- Buildings blocking heat from escaping/radiating into the relatively cold night sky.
- Buildings blocking wind, inhibiting cooling by convection.
- Tall buildings within many urban areas provide multiple surfaces for the reflection and absorption of sunlight, increasing the efficiency with which urban areas are heated.
- Lack of evapotranspiration (for example through lack of vegetation) in urban areas.
- Materials commonly used in urban areas for pavement and roofs, such as concrete and asphalt, have significantly different thermal properties and surface radiative properties than the surrounding rural areas.
- Changes in the thermal properties of surface materials that make them absorb and/or retain more heat.
There are causes of heating that we cannot avoid, for example, solar radiation. But nature also has its way of cooling, which happens during the evening. Because the air then is cooler, the heated objects on the surface of the earth would then transmit the heat into the night sky. But as mentioned, buildings could prevent this from happening. Vegetation (greenery!) such as in rural areas, or the "sea breeze" from adjacent large bodies of water (e.g. Manila Bay) could also help cool things down. But because we build and build roads and buildings and other infrastructure, there are then less and less opportunities for nature to help us cool down.
Now obviously, we can't really stop building roads and buildings and other infrastructure, especially in our developing country. We can't stop people from using cars and air-conditioners and building factories, and so on. But we can decide where to put these things, or how often to use them.
For example, prioritizing the construction of more comfortable mass transit infrastructure could help reduce pollution from cars. We could build buildings and homes adorned with a lot of greenery. If we build efficiently enough, we might be able to be less dependent on air-conditioning, and therefore lessen the amount of cooling we need.
But lastly, as I mentioned, we can decide where to build. Do we need to reclaim more land on the Manila Bay and allow a developer to build more buildings and infrastructure on the bayside? I would vote no to such. If you agree, sign this petition, will you please:
Now, I haven't personally seen what exactly are the plans for that development. Have they taken this into consideration? Actually, the petitioners are concerned with the blockage of the famous Manila Bay Sunset view, which is a valid concern. An even more pressing concern is the potential for trapping flood longer within the metropolis, because of the likely blockage effects from the reclamation, which could prevent flood waters from withdrawing out to the bay.
In any case, the UHI effect itself can be quantified through the use of some wind engineering techniques, and some mitigation can be applied. The wind engineering techniques involve, as always, the study of (micro-)meteorology, and bluff-body (i.e. building) aerodynamics, or flow around all these urban structures. Computational fluid dynamics (CFD) could be used, although they would need some physical validation. Wind tunnel testing, perhaps with consideration of thermal effects and not just wind, might prove to be useful, as it always does.
But in addition to the petitioners' concerns, here's the more troubling thought. Those UHI mitigation measures come in only two options:
- The developers do not proceed with the reclamation and the construction (which could be by way of law, like maybe a rejection of the project's Environmental Compliance Certificate application).
- We all accept all the consequences of the development of the said project (and similar ones), and do the mitigations by ourselves -- i.e. those of us building inland. Because we would need to install more greenery by ourselves, use less fuel for our transportation, and maybe use less air-conditioning. In a sense, this option is a tax on the rest of us who are not invested in the said project.
I'd vote for the 1st option. I hope you do, too. Again, please sign the petition, if hopefully I have already convinced you enough:
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