URBAN DISCOMFORT

Poorly planned, heat-trapping infrastructure, along with dwindling natural spaces, turn up the temperatures in major Indian cities

IN A warming world, urbanisation has a profound impact on heat. As a city's population grows, infrastructure needs to be developed to cater to its requirements.

Cities contribute more than two-thirds of global carbon dioxide emissions, according the UN Environment Programme. However, their environmental impact goes beyond emissions. As a city grows, the way buildings, roads and railways are laid out; the density, height and size of buildings, and the materials used; the amount of green spaces and water bodies; and level of human activities such as use of vehicles and airconditioners together determine how much heat is retained in the immediate area.

When released, this heat raises the temperatures of the nearby atmosphere. As the grey infrastructure gets denser and more concentrated, it erodes the natural spaces that act as heat sinks and keep the environment cool (see 'Influencing factors'). If left unchecked, such development could create an urban heat island effect, with cities recording high temperatures that can adversely impact the health of people, and also potentially be fatal.

To analyse the status of urban heat islands in the country and establish the ongoing heat burden that is a result of their development, Delhi-based think tank Centre for Science and Environment (CSE) conducted a study in nine cities-Delhi, Jaipur, Kolkata, Nagpur, Pune, Ahmedabad, Hyderabad, Chennai and Bhubaneswar.

These cities, which are of different sizes and are located in different climatic zones, show that the problem of heat is not restricted to a specific kind of climate or geography.