'Cool roofs' can beat high heat in homes

New Delhi : With India too facing the effects of global warming with abnormally high temperatures, simple and low-cost 'cool roof' measures may bring relief to the people, say experts.

"Simple steps such as painting roofs with lime-based whitewash, adding tarp-like coverings, or white ceramic tiles, can help bring down roof surface temperatures by 30 degrees Celsius and also reduce indoor temperatures by three to seven degrees," New York-based advocacy Natural Resources Defence Council's (NRDC) Director of India Programme Anjali Jaiswal told IANS.

She said the innovative low-cost cool roof projects in Ahmedabad and Hyderabad cities, piloted this year, were a great success.

Climate experts say 13 of the 15 hottest years in India have been recorded since 2002, with the highest temperature recorded in 2016. This summer, parts of India have experienced abnormally high temperatures in March and April. Heat waves occur from April to June, before the Indian subcontinent is awash with monsoon.

An NRDC interim report "Cool roofs: Protecting local communities from extreme heat" this month says less than 10 per cent of India's households have air conditioning.

With summer temperatures regularly exceeding 40 degrees Celsius (104 degrees Fahrenheit) in a majority of India's cities and large sections of population in low-income housing having little to no access to electricity, access to cooler homes is a matter of survival, not just comfort.

The report, quoting a research by the International Institute of Information Technology in Hyderabad and the Lawrence Berkeley National Laboratory, says 'cool roofs' could reduce peak energy demand by 10 to 19 per cent in buildings in Hyderabad.

This will potentially help reduce citywide air temperature by two degrees Celsius (3.6 degrees F) and save Rs 500 crore over 10 years, it says.

A new study, published in journal Nature Climate Change on Sunday, indicates nearly one-third of the global population currently gets affected by heatwaves and the figure could become "nearly three quarters by end of this century."

Another study published this month in the Science Advances journal, which is India specific, tries to link climate change to heat-related deaths.

It said as the mean summer temperature and the annual number of heatwave days increased in India from 1,960 to 2,009, there was a 'substantial increase' in heat-related deaths.

Some experts expect India's temperature to rise by 2.2 to 5.5 degrees Celsius by the end of this century, said the study based on India Meteorological Department (IMD) data.

The IMD defines a heatwave as when temperature on any given day is more than three to four degrees Celsius above normal at places where the usual maximum is above 40 degrees.

"India is showing the world that in our fight against climate change we can take smart steps right now to protect millions of people from deadly heatwaves. These groundbreaking heat action plans like 'cool roofs' also demonstrate that it's feasible to create similar heat preparedness plans across Indian cities," NRDC's India consultant Nehmat Kaur said.

Last year was India's hottest year on record -- 0.91 degree Celsius above the 1961-1990 average temperature, the IMD said.

Records began in 1901. Since then, India's average temperature has increased at a rate of 0.65 degree Celsius a century.

In Southeast Asia, 15 to 20 per cent of annual work hours may already be lost in heat-exposed jobs. This may double by 2050 as global climate change progresses, says a 2016 study by the US-based National Center for Biotechnology Information.