Think About The Earth

Cities in Hot Seat (1 of 2) August 26, 2009

“It’s so hot here in the Philippines!”

How many times have we heard this line from foreigners or balikbayans?  But now, we don’t hear this only from foreigners or balikbayans but from Filipinos who have been born and are living in this country.

And it’s not only in the Philippines that the weather is getting hotter every day.  The culprit?  Global warming.

Everywhere in the Philippines, environmental changes happen.  A study conducted by the Institute of Environmental Science and Meteorology of the University of the Philippines (UP) shows that the temperature in Metro Manila has become hotter than ever before.  And this is not all about global warming—there’s another story that contributes to this finding and that’s the urban heat island effect.

Heat in the City

Using satellite thermal images supported by air temperature records of the Philippine Atmospheric Service Administration (PAGASA), scientists from UP found out that air temperature in Metro Manila increased, compared to the adjacent rural places of Cavite and Bulacan.  This increased in temperature in thickly populated places relative to the surrounding rural areas is called the urban heat island (UHI) effect.  Average temperatures in places with UHI may reach up to 5.6 degree Celsius warmer than the surrounding countryside.

It was found out that Metro Manila’s average nighttime temperature in May 2007 was 2.68 degrees Celsius higher than that of Cavite and Bulacan.

Heat islands form as cities replace the natural cover of land  with cemented pavements, streets, buildings, and other structures.  This led to an increase I urban temperatures in a number of ways:

●  When trees and vegetation are displace the natural cooling effect of shading and evaporation of water from soil and leaves is diminished.

●  All buildings and narrow streets can heat the air trapped between them and reduce airflow.

●  Heat emitted by vehicles, factories, and air conditioners may add warmth to their surroundings, further intensifying the heat island effect.

Aside from these factors, the intensity of UHI effect also depends on the area’s weather and climate, proximity to bodies of water, and topography.