Adianto P. Simamora, Jakarta – Less trees, polluted, gluggy water and the heat from more vehicles is making the city's temperatures rise to scorching levels in the dry season, not global warming, the Meteorological and Geophysics Agency (BMG) says.
The agency says temperatures for the area in this year's dry season have averaged between 33 and 34 degrees Celsius.
"These are the normal temperatures in the dry season. What causes the city to feel hotter lately is purely environmental degradation," agency spokesman Ahmad Zakir told The Jakarta Post Saturday. "It is all human activities causing the city to become hotter," he said.
Driejana of the Environmental Department at Bandung Institute of Technology said human activities in urban areas had seriously increased heat pollution. "This is a phenomenon, an urban island of heat. It happens... when a city become warmer than its surrounding areas," she told the Post.
Driejana said heat islands were different from global warming, which increased average temperatures worldwide. Population increases in areas generally cause them to heat up, she said.
"As populations grow, the demand for infrastructure will increase; more open space will be exploited and it will weaken the quality of the environment," she said. "The presence of high-rise buildings in Jakarta blocks air circulation in the area, while the surface of the buildings are heat sources," she said.
The building absorb the sun's heat in daytime and give off heat as they slowly cool down after sunset, preventing a dramatic temperature drop at night. Driejana said that the increase of asphalt and concrete roads also helped trap heat in the city.
"The surface of black-colored asphalt absorbs the sun's heat just like people wearing black clothes. It why some countries have changed the colors of their roads," she said.
Australia, she said had adopted brighter colors on its road surfaces to cool cities down. The Jakarta administration, meanwhile, is building light gray-hued roads on several corridor lanes of its busway.
Driejana said that allocating more green zones in urban areas could significantly reduce radiated heat and help control air pollution. "Trees can insulate us from the sun's heat. They transpire moisture during the daytime making areas fresh," she said.
Jakarta experiences large daily fluxes in population – home to an estimated 10 million people at night, its numbers swell to 12 million in the daytime.
Most of its green zones have been converted to commercial premises or been illegally settled by poor migrants. Of it 60,000 hectares of land Jakarta currently has only 5,911 ha of green areas or 9 percent.
The administration has pledged increase green spaces of 9,156 hectares, or 13.94 percent by 2010. Many trees were recently cut down to make way for the city's busway and monorail projects.