Cities warming due to the combined effect of urbanisation, climate change

Sub: Geography

Sec: Climatology

Context:

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.

Details:

India’s urban population is projected to double by 2050, adding more than 450 million residents, surpassing the current total population of the United States and the European Union.
The urban heat island (UHI) effect makes cities warmer than rural areas by trapping more heat due to altered thermodynamic and aerodynamic properties.
Climate change is causing significant increases in record-breaking temperatures and prolonged heat waves, contributing to complex warming in cities.
This altered micro-climate affects heat, rainfall distribution, air pollution dispersion, and public health, necessitating scientifically informed urban planning.

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 where the heat is trapped and not able to dissipate easily.
Urban heat island is basically induced due to trapped heat between establishments made up of concrete.
The temperature variation can range between 3 to 5 degrees Celsius.

Study on warming effects:

A recent study sought to separate the warming effects of local urbanization and regional climate change in 141 major Indian cities.
The study used high-resolution night-time land surface temperature data from NASA’s MODIS sensor, comparing urban and rural temperatures from 2003 to 2020.
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.

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.

Source: TH