urban climate

It's been known for some time that urban areas create a heat island as the hard surfaces store more solar radiation than the vegetation they replace. Adding to the effect is the heat generated from within buildings, and changes in air circulation. Studies have suggested that the result is significant enough to change the growth cycles of plants in some cities by altering the growing season.

Now scientists studying climate in areas of rapid urbanisation in China are finding changes in rainfall linked to urban sprawl. They speculate that an observed decrease in rainfall may be related to loss of vegetation, and the fast rate at which water runs off city streets, reducing the transfer of water to the atmosphere.

A lot can be done to mitigate urban energy waste, heat buildup and water runoff: from the layout of urban areas and the incorporation of vegetation, to the design of buildings and their heating and cooling systems. Strategies should include not only consideration of the way buildings are designed, built and operated, but also new approaches in disciplines like transport planning, traffic engineering, urban design and wastewater management. Some short-lived guidelines started to address these issues during the oil crisis of the 1970s, but only in recent years have planning guidelines started to incorporate energy considerations again. There are examples in Australia and the US.

I have no doubt that Dongtan Eco-city and its offspring will establish new standards for the planning of low-carbon cities, but until these initiatives become common practice, we'll have to rely on the examples set by individual buildings and small districts within cities. Here's a list (with pictures) of ten tall buildings that incorporate strategies to reduce carbon emissions and other environmental impacts.