Every day global warming is setting new temperature records worldwide. Bangladesh is no exception. Just a few days back, the country experienced severe heatwaves, prompting ‘Heat Alerts’ and the closure of educational institutions. This situation seems to be worsening each day.
In April, temperatures across the country fluctuated between 36 to 43 degrees Celsius. This raises the question: What lies ahead? Will the ‘heatwave’ conditions continue to deteriorate, or can we do something about it?
Research from the University of North Carolina at Chapel Hill indicates that urban centres are generally 3 to 4 degrees Celsius hotter during the day than their suburban and rural counterparts, with night-time temperatures sometimes differing by 10 to 15 degrees Celsius. This phenomenon is also true for Bangladesh. For example, while daytime temperatures in Dhaka may reach 40 degrees Celsius, they drop to about 30 to 32 degrees Celsius at night. In Rajshahi, although daytime temperatures also reach 40 degrees Celsius, night temperatures drop to 22 to 24 degrees Celsius.
Professor Dr. Zillur Rahman from the Department of Disaster Science and Management at Dhaka University points out that humans are the primary contributors to environmental degradation, as we have significantly increased all the parameters leading to higher temperatures. Dhaka has been transformed into a city of concrete. During the day, these concrete structures and tarred roads absorb and retain heat. There’s hardly any shade, and we’ve drastically cut down trees and filled up water bodies, which exacerbates the heat retention even at night. The vehicles burning fossil fuels on our roads are also contributing to the rise in temperature. Additionally, the excessive use of air-conditioning units further aggravates the situation.
The Chapel Hill study suggests several measures to cool urban areas:
1. Reduce the use of personal vehicles to cut down on fossil fuel usage. Public transportation, particularly electric vehicles and bicycles, should be encouraged.
2. Construction materials should be chosen for their ability to reflect rather than absorb heat. Using natural materials like bamboo and wood, and applying thermoplastic polyolefin (TPO) on roofs, which reflects rather than absorbs heat, helps keep indoor temperatures cooler.
3. For apartment dwellers, creating rooftop gardens and painting roofs white can help reduce building temperatures through evaporation.
4. The government should take a leading role by implementing policies for rooftop gardens and white roofs. The example of New York City under former Mayor Michael Bloomberg, who mandated certain sections of roofs to be painted white and to have gardens, shows significant benefits.
5. Investing in urban heat emission management systems, such as covering roads with titanium oxide, which reflects rather than absorbs heat, should be considered.
6. Taking a cue from Singapore, buildings should be designed to facilitate airflow, which prevents heat from being trapped inside. Singapore also invests heavily in research to develop construction materials that do not absorb heat.
7. The use of fossil fuels should be minimized, and renewable energy sources should be promoted.
Dr. Ahmad Kamruzzaman Majumder, Dean of the Faculty of Science at Stamford University, emphasizes the need for short, medium, and long-term measures to control urban temperatures. These include promoting rooftop gardens and white roofs to reduce heat absorption and reducing the use of air-conditioning and fossil-fueled vehicles.
While immediate actions can provide temporary relief, long-term solutions such as planting more trees and restoring water bodies and canals are essential to sustainably reduce urban temperatures. Local geographical and environmental characteristics must be considered in urban planning to effectively tackle the heat.
