An archipelago of heat islands

An archipelago of heat islands

Pleasant weather, oh so perfect! That seems like a distant dream as the scorching summer heat has every Bengalurean scurrying for cover, wondering what’s going so badly wrong. But why raise an eyebrow, when the green cover depletes, water bodies vanish and concretization takes big, monster steps?

The city temperature, rising since late February, shows no sign of receding. Be prepared to endure upwards of 38 Degrees Celsius or beyond, warns the Karnataka State Natural Disaster Monitoring Centre (KSNDMC) director G S Srinivasa Reddy. “Temperature will be very high in April. The city has seen record highs hovering around 39 Degrees,” he explains.

The weather signs from the rest of Karnataka have been ominous, and this has a direct bearing on the heat felt in Bengaluru. “In February, we have seen average temperatures raising by 2-3 Degrees and even going beyond five Degrees in some areas. Right now, we see no systems that will bring rain to cool temperatures in the city,” notes Reddy.

38 Degrees and beyond

The implication is clear: The temperature will hit 38 Degrees by the third week of April. “Moisture levels this year are much lower than last year. By this time last year, the State had received about 36 mm of rainfall. Only 9 mm rainfall was recorded from April 1 to 11 this season. Humidity is low, and that makes people to perceive the heat to be much higher.”

But beyond changes in climatic patterns, two key factors clearly affect the local temperature. An Indian Institute of Science (IISc) study had established the correlation between rising temperatures and the decline in vegetation and water bodies. “These are heat sinks that absorb the heat and moderate the local climate,” explains Prof T V Ramachandra from the IISc Centre for Ecological Studies.

In the green IISc campus, the average temperature hovers around two degrees lower than the surrounding areas. This pattern repeats inside and outside the city’s parks and surviving water bodies. “Over the decades, the average temperature has been rising from 19 degrees to 21 to 23 to 36 degrees Celsius now.”

Hot glass facades

New building architecture with glass facades has been another key contributing factor. “Due to radiation from such glass structures, the temperature outside can touch 40 Degrees. This can be seen in areas such as Whitefield that has a multiplicity of such buildings,” Prof Ramachandra points out.

To understand the microclimate patterns better, KSNDMC has proposed to take up a month-long study across Bengaluru. “We have 10 monitoring stations in and around the city. Another 10 weather sensors will come up over the next two months,” informs Reddy.

Perhaps, the results might give an accurate understanding of the city’s changing weather patterns, which once meant cool breeze even during summer. The massive, unregulated destruction of the city’s green spaces and lakes has now reduced old Bengalureans to get nostalgic of a pleasant past.

“We see consistent, exponential erosion of the environment year after year, which is directly reflected in the weather. Earlier there used to be shower spells during Shivratri, Ugadi, which are dearly missed today. It is clear that there is a shift happening,” notes Vishnu Prasad, a resident of Bellandur for over 10 years.

Prasad suggests a potential remedy: Let every citizen grow and nourish at least five trees. This, he hopes, can help the environment and cool temperatures in the long run.

Heat islands

Friends of Lakes founder Ram Prasad notes that Bengalureans themselves have created heat islands. “Many people from other States came to Bengaluru only for its excellent weather. But the city will soon turn into Chennai and Delhi soon,” he notes.

He adds with concern that the massive destruction of water bodies has become a serious concern but no bureaucrat or policy maker talks about it.

Sarjapur Road resident Chandan Reddy notes how the switching on of the air conditioners at office is a sign that summer has set in. This, he says, is becoming quicker year by year. “Indeed, the temperatures soar ever year because of the choices we have made for our comfort.”

AC sales

Air-conditioner sales have been soaring this season. This is also a sign of the times, as old Bengalurean, Ravi Kumar puts it. “I have lived in the city for more than 50 years now. I remember those summers when we would sit under trees to play games now considered indoor.”

Kumar does not remember a single summer day when an AC set or even a fan was considered necessary. “But over the past few years, the heat has forced us to remain indoors, under the comfort of fans and ACs,” he laments.

Spike in paved areas

Over a decade ago, an IISc study had conclusively proved the spike in Land Surface Temperature (LST) due to land cover changes between 1973 and 2007. The analysis showed that a 466% increase in paved surfaces (buildings, roads, etc.) had resulted in LST increase by about 2 ºC during the studied period. This confirmed urban heat island phenomenon.

However, the LST was relatively lower (4 to 7 ºC) where land was under vegetation (parks/forests) and water bodies that act as heat sinks. In the 12 years since this study, Bengaluru has seen phenomenal but mostly unregulated growth in concretisation, an explosion of vehicular population and a seriously unhealthy spike in pollution.