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Big Indian cities stare at acute heat spells, rise in pollution: Report

An IPCC report states that there are lower risks projected for heat-related morbidity and mortality in case of 1.5-degree rise compared to a 2-degree rise in global warming. But urban heat islands will often amplify the effects of a heat wave in cities, the report says.

india Updated: Oct 09, 2018 07:59 IST
Jayashree Nandi
Jayashree Nandi
Hindustan Times, New Delhi
heat spell,pollution,IPCC
A heat map developed by Carbon Brief based on IPCC projections suggests Delhi has warmed by 1°C so far and may experience a warming of 1.3°C to 5.2°C by 2100 depending on how emissions continue to grow. (HT/File Photo)

Big cities in India are likely to experience severe heat spells and air pollution if global warming rises more than 1.5°C compared to temperatures seen before the industrial age, according to authors of the Intergovernmental Panel on Climate Change (IPCC) report titled Global Warming of 1.5 degrees.

Scientists responding to the report said Indian cities are already suffering severe air pollution and will not be able to adapt to any higher levels.

Though the report does not have country-wise projections, Joyashree Roy, professor of Economics at Jadavpur University and co-author of the report, said: “Heat stress in cities and rising air pollution are two impacts we are definitely going to see. This is because of increased fossil fuel use for energy like diesel, coal and biomass burning.”

The report states that there are lower risks projected for heat related morbidity and mortality in case of 1.5-degree rise compared to a 2-degree rise in global warming. But urban heat islands will often amplify the effects of a heat wave in cities, the report has said.

“Without considering adaptation options, such as cooling from more reflective roofs, and overall characteristics of urban agglomerations in terms of land use, zoning and building codes, at 2°C warming, Karachi and Kolkata could expect annual conditions equivalent to the deadly 2015 heat waves,” said a chapter of the special report.

A heat map developed by Carbon Brief based on IPCC projections suggests Delhi has warmed by 1°C so far and may experience a warming of 1.3°C to 5.2°C by 2100 depending on how emissions continue to grow. If there is an effort to keep global warming under 2°C globally, then Delhi may experience a 1.3°C rise. Delhi already has several heat islands, according to research studies by Indian Institutes of Technology (IIT) Delhi.

An urban heat island is usually an area significantly warmer than its surroundings. Surfaces made of concrete that used to be otherwise permeable and moist start radiating heat, forming an area of high temperature.

“Increasing temperature and air pollution work like a vicious cycle. When there is more heat, cooling energy needs increase. More energy use leads to higher emissions and pollution. It has a cascading effect,” said professor Manju Mohan of Centre for Atmospheric Sciences at IIT Delhi. She added that ozone emissions are also higher due to heat because ozone is produced from chemical reactions between oxides of nitrogen (NOx), volatile organic compounds (VOCs) and carbon monoxide (CO) in the presence of sunlight and heat.

Professor Sagnik Dey also from CAS is currently working on a project on various climate change scenarios and air pollution levels. “There is a two-way connection between air pollution and climate change. One is that aerosols like black carbon (BC) have global warming potential. Secondly, global warming will lead to increase in temperature, change in rainfall, humidity will affect pollution transport and various other atmospheric processes. We are studying these changes,” said Dey.

First Published: Oct 09, 2018 07:54 IST