URBANIZATION DRIVEN WARMING :
Context :
Cities in India are experiencing warming at nearly twice the rate compared to the rest of the country, according to a recent study published in the journal Nature.The study found that cities in India are warming at an average rate of 0.53°C per decade, with urbanisation contributing 0.2°C. Urbanisation is contributing the increase in warming 60%. Study done by IIT, Bhubaneswar published in nature.
The researchers ranked 141 cities based on warming attributed to climate change (regional effect) and urbanisation (local effect).
In cities such as Jamshedpur, Raipur, Patna, Indore, Bhilai, Aurangabad, Pune, Dhanbad, Ludhiana and Vadodara, urbanisation contributed more than 50% to overall warming. In particular, urbanisation contributed to 100% of the warming in Jamshedpur.
“The urban contribution is seen to be higher in cities in the eastern and central Indian regions, One possible explanation could be that these (eastern and central Indian) cities have gained momentum in urban growth in recent years, and hence, the rate of growth at which heat is trapped within these cities is higher than the older cities that are already large, and hence, the rate of growth is smaller.
CAUSES OF WARMING INDIAN CITIES
Urban heat Island effect
Regional climate change or global warming
Urban Heat Island:
Urban heat island may be defined as the local and temporary phenomenon in which certain pockets within a city are experiencing higher heat load than its surrounding area.
This rise of heat basically happens due to buildings and houses of cities made up of concrete and roads and pavement made up from Asphalt where the heat is trapped and not able to dissipate easily.
Irregular height of buildings trapped the outgoing heat waves(IR waves) called urban canyons effect.
Lack of vegetation cover and water bodies due to congestion , lack of open spaces , natural cooling effect reduces.
Heat released by urban activities by vehicles, industries, commercial and household heating and cooling activities such as carbon emissions and other pollutants.
Reduced green and blue spaces on ground increases the surface runoff and reduces evaporative cooling rates.
More absorption of solar radiation by low reflectance/albedo materials used in construction such as concrete/asphalts,steel,etc referred to as high thermal inertia materials.
All the above factors and processes develops the urban heat plumes and urban heat dome that raise the temperature of urban areas both in day and night time than the rural areas.
Urban heat island is basically induced due to trapped heat between establishments made up of concrete.
The positive thermal anomalies within cities remain higher between 3 to 5 degrees Celsius and may reach to 10 degree celsius.
By 2050, India’s Urban growth led to an additional 450 million people to cities i.e., 68% of urbanization level by 2050.
Regional global warming induced by human induced climate change : greenhouse gases emission :
Climate change is causing significant increases in record-breaking temperatures and prolonged heat waves, contributing to complex warming in cities.
According to the Global Climate Risk Index 2021, India is the 7th profound impacted country in the world due to climate change extremes like heat waves,etc
Impacts of warming of cities by combined effect of urbanisation and climate change :
Results showed that the rate of warming in cities is nearly twice that of the rest of the country, with urbanization alone causing additional warming of about 60%.
An average increase of 0.53°C per decade in night-time land surface temperature was observed, with tier-II cities in eastern India experiencing stronger urbanization-driven warming than larger metros.
Recently, Delhi experienced daytime temperatures above 50°C for two consecutive days, the highest ever recorded in the city.
Cities are experiencing higher temperatures due to ongoing climate change and rapid urbanization, which are defining the Anthropocene.
Heat waves in cities causing poor air quality, increased heat related health issues like cramps, heat stroke,death, dehydration,
Economic loss due to infrastructural damages, labor productivity loss, fires in buildings,etc
Mitigation measures against cities warming :
This altered micro-climate affects heat, rainfall distribution, air pollution dispersion, and public health, necessitating scientifically informed urban planning.
India’s efforts to reduce warming effects:
India is actively reducing emissions and shifting to non-fossil fuel energy sources, as outlined in its updated nationally determined contribution (NDC) for climate justice.
State-level heat action plans and early warning systems for heatwaves show India’s commitment to reducing heat-related mortality.
Recommendations:
Tailored city-specific action plans are needed for sustainable urban growth, considering the predominant contributors to warming.
Urban heat management should follow a differential approach:
local-scale interventions (cool roofs, green infrastructure, urban forests) for cities with high urbanization contributions, and
regional-scale efforts (large-scale afforestation, rejuvenation of water bodies) for cities with higher climate change impacts.
Pollution control norms through policy interventions like shifting industries away from cities, e-vehicles, clean and green fuels, absorption of greenhouse gases,
Heat action plans ready like mapping and zoning of core areas, early warning, cooling public places & shades, water availability, hospital preparedness for emergency.
Urban planning components includes garden city concept, urban forestry, smart and sustainable cities, open spaces for green and blue infrastructure,
Geo-engineering methods like whitening of roads and roofs, urban canyon reduction by design of building and its heights, solar tiles, material of construction changed to be more reflective, lower interia, higher albedo,etc.
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