Heatwave days to double in Chennai, Avadi, Tambaram; 21 cities in Tamil Nadu to feel the burn

CHENNAI: If the heatwave this year was unbearable, buckle up, as the number of heatwave days will double before 2050 (26 years) in 21 cities across the State including Chennai, Tambaram and Avadi.

Making the situation worse, Chennai has a green space deficiency of 62 sq km.

According to a draft report titled, ‘Climate Risk Assessment and Adaptation Plan of Tamil Nadu – Sustainable Habitat’ prepared by the Centre for Climate Change and Disaster Management (CCCDM) in Anna University (1990-2020), escalating thermal discomfort conditions, particularly in the northern coastal regions, have significantly impacted urban areas.

Projections indicate a concerning trend of increasing thermal discomfort days, reaching up to 250 days per year by the Near Century (2050). “City Climate Risk assessment highlights that the cities in the northern coastal regions such as Greater Chennai Corporation and the surrounding areas of Avadi, Tambaram are exposed to high levels of climate hazards. Tirunelveli, Tiruchy, Thanjavur, Kumbakonam, Madurai, Sivakasi, Dindigul, Nagercoil, Kancheepuram, Thoothukudi, Cuddalore and Salem are at moderate risk to climate change while Karur, Tiruppur, Hosur, Coimbatore, Erode and Vellore face low risk,” the report added.

Saying that the intensified urban heat island effect and temperatureextremes place urban areas at risk, the study said that Chennai, Nagercoil, Thanjavur and Thoothukudi have experienced more than 40 days with heatwaves per year on average during 1985-2014. The number of heat wave days is projected to double during the nearcentury.

If the maximum temperature is more than 4.5 degree Celsius than the normal temperature, the Indian Meteorological Department calls it a heatwave.

Annual average heatwave days in Chennai will increase to 81 days from present 42 days. Similarly, annual average heatwave days in Avadi and Tambaram will increase from 43 and 42 days to 80 and 78 days respectively. Kancheepuram, which has 39 heatwave days, will have 74 heatwave days by 2050, as per the study.

Of all the 21 cities, which will face a higher number of heatwave days in the future, Chennai would be the most affected. “The overall exposure assessment reveals that Chennai, with highest population density and high population of homeless people, is the most exposed city in Tamil Nadu. Poor infrastructure and socio-economic factors make these groups more vulnerable to heat stress and related illnesses,” the report said.

Attributing the occurrence of higher number of heatwave days to lack of green cover, the study said that Chennai has a green space deficiency of 62 sq km, which is the highest among the 21 cities, as per the Urban Greening Guidelines, 2014.

For around 438 sq km of the total area, Chennai has only 8 sq km of green cover against the recommended requirement of 79 sq km. Further, 9 sq km has a potential for additional green cover.

Coimbatore has only 7 sq km of green cover against the recommended 60 sq km. The city has an additional potential of 13 sq km but a deficiency of 40 sq km. On the other hand, Avadi has a deficiency of 5 sq km.

Interestingly, Kancheepuram and Tambaram along with Nagercoil have nil deficiency. Under the Urban Greening Guidelines, the Ministry of Urban Development recommends that the proportion of recreational areas, including parks, open spaces, waterbodies and others, to the total developed area in medium towns and large cities should be from 18-20%. In metropolitan cities, the proportion should be 20-25%.

“In this situation, it’s vital to enhance the green cover in cities with the lowest per capita green spaces. The cities with more than the recommended green cover must be preserved without further degradation due to the ever-growing population in the future. Though urban forestry is man-made, the results inferred that more attention must be given to urban forestry management,” the report recommended.

On the other hand, the increasing temperature and heatwave would affect the growth of plants and biodiversity due to the reduction in isothermality (the degree to which temperature varies throughout the year). Isothermality ranged from 51 to 67 across the cities of Tamil Nadu during 1985-2014, which reduced to 48-65 in the near century.

A reduction in isothermality will lead to higher daytime temperatures within cities. “Elevated temperatures worsen air pollution. Chemical reactions in the atmosphere increase smog formation and ground-level ozone,” the report said.

The State Environment, Forest and Climate Change Department is drafting an Urban Greening Policy to increase green cover in the cities. “The policy for the entire Tamil Nadu will cover the various aspects of greening the city through creation of urban parks, avenue planting, vertical gardens, green belts around the industrial areas,” a senior environment department official said.

The official added that the urban policy on greening will be a part of the Green Tamil Nadu Mission. For the implementation, there will be a dedicated wing in cities and corporations composed of botanists, horticulturists, landscape architects and others.

Green space required (in sq km)

Annual average heat wave days