Climate Matters. U is for Urban heat islands

This post is for U in the A-Z Blogging Challenge 2012. Link in the sidebar.


Central business districts in cities and dense industrial zones store heat in the buildings, roofs, roads and paved surfaces during hot days. This is called the urban heat island effect. As a result, these areas can be up to 10 degrees Celcius hotter than surrounding areas. The heat may be released slowly overnight, so they’re often warmer than less densly built up areas or parks and gardens and rural environments.

Summer heat is absorbed by dark buildings, trapped and
released back into the city at night, preventing cooling.

When we have cloudy nights, this acts as a blanket, because the tall buildings are crowded together, there are less breezes to disperse the heat, so it's trapped.

In addition emissions from vehicles, industrial activity and air conditioning vents contribute to the warming in cities. This can be welcome in cold winters, but during the summer it can leave citizens sweltering uncomfortable and for many including the elderly, young and ill it can be extremely dangerous.

It’s been suggested that reading temperatures from these unusually heated areas could distort climate data, but although some weather stations are located in cities, many are in remote locations, small towns and regional centres as well. The extensive data collected balances out any localised anomalies, and when added to data collected worldwide, there is evidence of consistent change in climate patterns over an extended period.

There’s a saying in Australia on extremely hot days “It was so hot you could cook an egg on a shovel”, and whilst that expression is unlikely to be used during a New York heat wave, it has been reported that temperatures reached on some asphalt roofs during one heat wave were almost hot enough to cook a chicken – that’s hot!

Green spaces in cities are cooling and create areas to meet friends and relax.

One simple and effective ways to cool cities, lower electricity usage and reduce the city’s carbon footprint is to plant rooftops with grasses or paint them white to reflect heat. Replanting city and urban landscapes with appropriate trees and plants is known to reduce the unpleasant sweaty and stifling effects of living in cities during heat waves. They not only add an immediate cooling effect, but encourage birds and insects and create a positive place for people to meet.

Some enterprising apartment dwellers create rooftop vegetable gardens and others use their balconies for vertical gardens for fresh herbs and vegetables giving them somewhere to use the output from their Bokashi bin and supplement their diet with fresh home-grown produce. 



Last year I wrote about the importance of Underestimating the Unrelenting nature of workplace bullying for U Here and a drabble about Unwanted attention here.


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