Climate change may make Delhi, Kolkata 2-4 degrees warmer: Study

New Delhi, Oct 10: Climate change could expose up to 2.2 billion people in India and the Indus Valley to many hours of heat that surpass human tolerance by the end of the century, a new research in Proceedings of the National Academy of Sciences (PNAS) said on Tuesday.

Researchers modelled global temperature increases ranging between 1.5 and 4 degrees Celsius to identify areas of the planet where warming could lead to heat and humidity levels that exceed human limits. Heat stress increases in magnitude and extent with every degree of global mean surface temperature increase, with monsoon dynamics likely to exacerbate heat conditions in South Asia and East China.

While impacts are concentrated in eastern Pakistan and the Indus River Valley in northern India in the 1.5 and 2 degrees Celsius warming scenarios, they expand in the 2 and 4 degrees Celsius warmer world, with a substantial accumulation of annual hot hours in the highly populated cities of Delhi, Kolkata, Shanghai, Multan, Nanjing and Wuhan.

With increased global warming, the regions that will experience the first moist heat waves and subsequent substantial increases in accumulated hot hours per year are also the regions with the largest concentrations of the world’s population, specifically those in India and the Indus River Valley (population: 2.2 billion), eastern China (population: 1.0 billion), and sub-Saharan Africa (population: 0.8 billion).

If emissions continue in their current trajectory, middle-income and low-income countries will suffer the most. This also reflects the large populations in South and East Asia, which, in a world that is 4 degrees Celsius warmer than the preindustrial period, is projected to experience around 608 and 190 billion person-hours of threshold exceedance in humid conditions, respectively.

If global temperatures increase by one degree or more than current levels, each year billions of people will be exposed to heat and humidity so extreme they will be unable to naturally cool themselves, said the interdisciplinary research from the Penn State College of Health and Human Development, Purdue University College of Sciences and Purdue Institute for a Sustainable Future.

Results indicated that warming of the planet beyond 1.5 degrees above preindustrial levels will be increasingly devastating for human health across the planet. Humans can only withstand certain combinations of heat and humidity before their bodies begin to experience heat-related health problems, such as heat stroke or heart attack. As climate change pushes temperatures higher around the world, billions of people could be pushed beyond these limits. Since the start of the industrial revolution, when humans began to burn fossil fuels in machines and factories, temperatures around the world have increased by about one.

In 2015, 196 nations signed the Paris Agreement which aims to limit worldwide temperature increases to 1.5 degrees above pre-industrial levels. The researcher team modeled global temperature increases ranging between 1.5 and four degrees — considered the worst-case scenario where warming would begin to accelerate — to identify areas of the planet where warming would lead to heat and humidity levels that exceed human limits. “To understand how complex, real-world problems like climate change will affect human health, you need expertise both about the planet and the human body,” said co-author W. Larry Kenney, professor of physiology and kinesiology, the Marie Underhill Noll Chair in Human Performance at Penn State and co-author of the new study.

“I am not a climate scientist, and my collaborators are not physiologists. Collaboration is the only way to understand the complex ways that the environment will affect people’s lives and begin to develop solutions to the problems that we all must face together.”