Heat on Mumbai’s towers

As Mumbai grapples with another heatwave this weekend, the focus is back on the built environment – and rightly so. This time the caution has come from none other than the Indian Meteorological Department (IMD) whose officials have stated that the rising maximum temperatures in the city have to do, among other factors, with the surge in highrises which trap heat for long periods and contribute to the urban heat island effect. The IMD caution is the strongest pointer that has come on the issue after the 2015 study which definitively outlined the urban heat island effect in Mumbai in which temperatures in an urban area are higher than its surrounding areas that are greener and have less concrete.

The last few days have seen maximum temperatures touch 40 degrees C. The IMD has forecast heatwave conditions this coming weekend not only in Mumbai but also in Thane and parts of Raigad. A heatwave usually signifies a maximum temperature of above 37 degrees C and where the departure from the normal maximum temperature is more than 4.5 degrees C. However, two aspects are usually ignored. One, is that Mumbai has seen a distinct difference between air temperatures and the Heat Index – usually of 4-6 degrees C – which factors in the relative humidity too. This means people are struggling in what feels like well above 40 degrees C on days that record even 37 degrees C. Secondly, the city is yet to draw up and implement a protocol for heatwaves as it has done for floods including an early warning system.

However, the crux of the problem is the rampant construction during which the city’s green areas and open spaces are being taken over for ‘development,’ the concretization which makes surfaces impervious to water percolation and trap heat, and the construction materials used. To make Mumbai cooler, in the literal sense, the authorities will have to review building bye-laws and codes to make all construction eco-friendlier and plant more trees.