Dirty fuel, urban heat island effect making heatwaves unbearable

The mere mention of ‘Heatwave’ stirs nervousness, scare and panic across the city administrations and residents of Karachi alike, rekindling the haunting memories of the over thousand deaths during ten days in June 2015 when the temperatures shot up to 44.8 degrees Celsius.

In the last 60 or so years, the temperature of the megapolis has increased by 2.25 degrees Celsius primarily being the major fossil fuels consumer and a huge contributor of CO2, which is the major heat-trapping Green House Gas, due to unprecedented growth in population, fuel-guzzling industry and vehicles and little vegetation cover. The increasing quantum of CO2 is directly proportional to the temperature rise in Karachi goes on to prove how the heat trapping Green House Gases (CO2, carbon monoxide, ozone, methane and nitrous oxide) are stimulating the global warming trends leading to disastrous climatic changes across the world. Heatwaves are just one of their several manifestations.

The World Meteorological Organization describes heatwave “when the daily maximum temperature for more than five consecutive days, exceeds the average maximum temperature by 9 degrees Celsius.” While one always experienced blistering temperatures from April to Oct and heatwaves too, but those were nothing as compared to the heatwaves that are striking with greater frequency and intensity nowadays. Meteorologists confirm four to five heatwaves lasting 5-10 days are more common now than six decades ago. Climate models predict a further rise in the frequency and intensity of the life threatening heatwaves towards the end of the century if nothing is done to drastically to slash the concentration of the CO2 and other Green House Gases that continue to increase by introducing cleaner fuels. One of the ridiculous ideas to curtail fuel cost was proposed by the government’s energy and fuel department was to let low quality but harmful fuel for motorbikes be allowed. While globally the tendency is to discard dirty, low quality fuel, our government ‘geniuses’ are defying scientific facts. Wouldn’t it be much better to more allow hybrid and electric vehicles to slash fuel cost by hundreds of billions and keep air free from toxins and heat being churned out every minute across Pakistan. This contribution to heat waves poses serious health hazards ranging from heat exhaustion to heat stroke while aggravating existing medical conditions like diabetes, respiratory complications, kidney and heart diseases. While the heat wave warnings do appreciatively drive the government and several volunteers to anticipate for medical emergencies by setting up water and cooling centers, but it is more like addressing the symptoms and not the underlying causes. The bigger challenge is the Urban Heat Island (UHI) effect that turns the cities into giant ovens spread every half a km particularly city centers with narrow streets and high rises on both sides curtailing wind circulation. The global warming has further increased the UHI effect too.

The buildings, roads, and pavements absorb heat and solar radiations. “The heat gets trapped in the city and gives the effect of an urban heat island on land.”Furthermore, at night, the absorbed heat is released into the atmosphere warming the denser city more than its surrounding suburban or coastal areas and strengthen the phenomenon of UHI. The wasted heat, like from ACs, is another source of additional heat being released into the atmosphere. Cameras using thermal imaging show buildings glowing orange and red at night with the heat from the ACs which also adds to the ambient temperature. This is a global phenomenon. Besides countless industrial and cluttered cities, New York city, London, Mumbai also average 1-3 degrees C warmer than their surrounding countryside. Karachi, Lahore, Peshawar, and Islamabad suffer from varying degrees of UHI effect too. At an average, their temperatures in the city centers ranges up to three degrees Celsius from the peripheral areas. For example if in any of the major city’s outskirts have 41 degrees Celsius, people at the centre of the city would be braving 44 degrees Celsius.

Suffering from criminal neglect Karachi with a population of 22 million continues to grow haphazardly is especially vulnerable as it resembles a huge mound of concrete plastered in the most grotesque fashion with a dwindling vegetation. Relative to the size of the massive expanse of the city there is only two percent green cover or inland water bodies to offset the scorching heat. The dense, city center comprises narrow streets and high rise commercial and residential areas where congested traffic belches up smoke, heat, and pollution, portraying the ‘Grand Canyon of heat and toxin’, says Senior Environmental Advisor Rafiul Haq. In many such areas generally a cloud of smoke hovers during rush hours making the residents and those who work there more vulnerable to asthma and other complex respiratory ailments. Badly ventilated buildings further choke up breathing.

Apart from odds for health, the increasing heat also severely challenges the power generation. As a rule of thumb, for every one degree Celsius rise, the electricity demand increases by 2-4 percent. Thereby for up to a rise of 3 degree Celsius as much as 5-10 percent power generation would be needed to cool it, increasing the requirement for power generation infrastructure as well as multiplying the fuel cost.

Different countries have employed different mitigating options ranging from painting surfaces white, planting more trees, creating green roofs to cool down neighborhoods. But one solution does not fit all the scenarios. Planting trees and converting paved areas to grass was also more effective than green roofs. And painting tar roofs white could also help to reflect solar radiation which has been legalized by New York since 2012.

Chicago’s experience at a smaller scale with increasing reflectivity helped it to cut down incessant heat from the UHI effect by 1.6 percent, equivalent to the cooling power of 65,000 large, window-sized air conditioning units operating at full capacity over the summer.

But this solution applied at a large regional scale has some negative aspects too. Too much reflectivity, white coating, can interfere to slow local sea breezes, reduce air quality and cut down rains too.

Only a detailed analysis of the hot spots and vulnerabilities coupled with reducing transport density, opting for quality and sustainable transport using cleaner fuels, incentivizing tree plantings, cool roofs, and cool paving materials can address the urban heat island effect. One guaranteed solution would be a 25 percent green canopy cover for Karachi to address the onslaught of the increasing heat stress.