Heat waves may hit North India most by 2100: Study

North India, along with parts of Pakistan and Bangladesh, would be among the regions hardest hit by climate change by the end of the century if the business as usual situation of greenhouse gas emissions prevails, a study published in the journal Science Advances said on Wednesday.

The hot and humid temperatures in the Indo-Gangetic Plains (IGP), home to over 900 million people, would exceed the upper limit of what normally people can tolerate, leading to higher mortalities due to heat waves, said a team of researchers led by Elfatih Eltahir, a professor of climate and hydrology at the Massachusetts of Institute of Technology (MIT) in the US.

In 2015, India and Pakistan witnessed one of the severest heatwaves in history which killed over 3,500 people.

The new findings they said were based on detailed number crunching using the best available global circulation models. The scientists came to this conclusion by assessing the vulnerability of people living in the IGP to withstand hot weather’s most deadly effects that stem from a combination of high temperature and high humidity, an index which is measured by a reading known as wet-bulb temperature.

It is said that human exposure to wet-bulb temperature around 35 degrees Celsius continuously for a few hours can result in death . A previous study of temperature and humidity records had shown that in today’s climate, wet-bulb temperatures have rarely exceeded about 31 degree Celsius anywhere on Earth.

“Under the business as usual scenario of greenhouse gas emissions, the crescent extending from Pakistan, North India and into Bangladesh would define a region where the intensity of the hazard caused by climate change (heat waves) and the acute vulnerability of the human population would converge, presenting extreme risks due to climate change,” Eltahir, who is the Breene M. Kerr Professor of Hydrology and Climate at MIT, told BusinessLine .

However, he also said that “these are quite avoidable and preventable if we adopt moderate mitigation measures.” “This could quite possibly happen. Heat waves are far more easy to simulate as compared to rainfall projections,” said Raghu Murtugudde, India-born earth system scientist at the University of Maryland, who is currently at the Indian Institute of technology Bombay as visiting professor.

As of now, only 2 per cent of the Indian population gets exposed to extremes of 32-degree wet-bulb temperatures, that too only occasionally. But this is projected to increase to 70 per cent of the population by 2100, according to the current study. About 2 per cent of them will be exposed to 35 degrees, which is uppermost survivability limit, said Eltahir in a statement issued by MIT. A 2015 study by Eltahir’s team looked at projected heat waves in the Persian Gulf region while the number of extreme-heat days projected for that Persian Gulf region was even worse than for South Asia.

But, the impact would be worse in South Asia. This is because the areas are among the poorest in the region, with much of the population dependent on subsistence farming that requires long hours of hard labour out in the open and unprotected from the sun. The Persian region, on the other hand, is relatively small and inhabited by wealthy population, said Eltahir.