NEW DELHI: Water bodies have decreased by a steep 40% in the national capital region (NCR) as a result of rapid urbanisation between 1972 and 2014, when the region saw a 17-fold rise in urban built-up areas, a study has revealed.
At certain places, the complete transformation into an urban environment has led to an increase of 3 to 5 degrees in land surface temperature and 2 to 4 degrees in air temperature during this period, the study by the Centre for Atmospheric Sciences at IIT Delhi found.
The study raises serious questions on the way urban planning was conducted in satellite towThe spatial coverage of urbanised areas, where temperature rise was seen, grew with every decade during the 42-year periodns around Delhi.
The spatial coverage of urbanised areas, where temperature rise was seen, grew with every decade during the 42-year period, the study published in Springer Nature’s Theoretical and Applied Climatology revealed.
The assessments were done by tracking the land use change in NCR for five years representative of 5 decades – 1972, 1981, 1993, 2003 and 2014 – using satellite images. The impact on meteorology was examined using a weather research and forecasting (WRF) model.
The study drew the example of Sariska National Park in Alwar district to illustrate the way forests were degraded in the region. Sariska saw a massive reduction in green areas over the years. From 240 sq km in 1972, its expanse reduced to 160 sq km in 2014, a decrease of about 33% of forest cover. “The dense tree canopies are replaced by shrub lands and sparse vegetation,” the report states.
Increase in land surface temperature has also led to a reduction in diurnal temperature range (difference between daily maximum and minimum temperature) by about 2 degrees in some areas while an increase of 1.5 degrees in night temperature was seen in some places.
The authors also note that increase in temperature over urban centres and sprawl areas was greater than what has been assessed by the Intergovernmental Panel on Climate Change (IPCC). As seen in this study, temperature rise can be as high as 1.5 to 2 degrees in highly urbanised areas as compared to the 0.6-0.9 degree rise predicted by IPCC in 2015. “Furthermore, after due consideration to anthropogenic heat, greenhouse gases and other pollutant emissions, estimated increase in temperature here is most likely going to exacerbate,” authors conclude.
“When green areas are converted to built-up areas the soil moisture available is lost. The thermal properties of built up areas are very different, there is more heat availability. We have noticed a complete change from crop land to urbanised areas in certain parts,” said Manju Mohan, head of CAS and lead author of the study.
