SciSun: The Heat is On   Leave a comment

‘Urban Heat Island’ is not a new reality show where singles compete for prizes and love (This week on ‘Urban Heat Island’ – Brendan comes one step closer to being burned; things are starting to heat up between Tony and Cristina; and can Jackie survive without being flamed?!?). No, the Heat Island Effect is the temperature effects within and radiating from developed areas; particularly cities where the man-made environment of brick, cement, asphalt and car traffic overwhelms the natural cooling provided by grass, trees and natural, vegetative landscaping resulting in a climate degrees warmer than the surrounding environment. For decades scientists (as well as anyone walking in a crowded downtown) have known that temperatures are often warmer in an urban environment; but only recently has research shown how even a small change in the amount of development can make a big difference – both in how hot, and how cool, a city can be.

Cities filled with ‘impervious surfaces’ – usually man-made products such as concrete that are great for buildings and sidewalks but poor for allowing sun and rain to reach the soil – also act as storage heaters, holding heat energy far longer than natural surfaces or other construction products such as glass, wood and many types of metal. A recent NASA study using satellite and temperature data (they’re not just about far-off stars and galaxies!) has discovered that when the area of impervious surface reaches just 35% of the total measured area – such as a town or city – urban temperatures begin to rise, continuing upward as more vegetation is lost. Generally any developed area is about 1 – 2 degrees warmer than surrounding countryside filled with trees and plants; once urbanization reaches 35%, city temperatures begin to rise until at 65% urbanization it’s often 3 – 4 degrees warmer. That might not sound like much, but based upon typical use one degree is enough to urge people to use 20% more air conditioning; walk and bike less but travel more by car, creating even more heat and exhaust; and increases water use while at the same time resulting in less water being available due to evaporation.

Sometimes, it's better to keep cool than to worry about your self-dignity.

Sometimes, it’s better to keep cool than to worry about your self-dignity.

Yet, in an attempt to combat the historic drought, today many cities, commercial centers, and individual home owners are ripping out lawns; cutting down trees; and replacing vegetation with rocks, cement, or leaving the bare earth. While reducing the amount of water use is very important – particularly in California and parts of the west where wildfires are burning through tens of thousands of acres due to dry, parched conditions – removing vegetation that collects and holds in water, releasing the excess through a process called evapotranspiration which adds cooling and humidifying water vapor to the air, is a contradictory action that might be well meaning but ultimately contributes to local warming and dry, barren environments.

While every city is, to some extent, a heat island – particularly population centers along the East and West coasts (we’re looking at you, Los Angeles!), and large metropolitan areas in the center of the country – ironically, not all cities, despite the heat island effect, are warmer than their surrounding natural environments: Cities in the desert which add trees and vegetation to areas where there had been none before often have lower temperatures than the surrounding region, making the cites, while still hot, a somewhat more pleasant area to live than a treeless desert community. As long as you remember, it’s a dry heat.


Michonne Says: I know it’s hot but that’s because marmots live around rocks. It’s a lot safer. We could live in the trees where the wind blows and there’s lots of nice leaves to sit under, but there’s already enough squirrels and birds in the trees as it is. And marmots can’t fly.

Posted September 20, 2015 by ECOVIA eco-adventure® in SciSun

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