A new study has projected a grim prospect, particularly for the South Asian region. The details sketched out by the research state that with a global 2°C rise, this region’s exposure to deadly heatwaves would become more frequent – in fact, it is expected to triple compared to the current exposure! Moreover, even if the mercury levels in the region are limited to 1.5°C, the impact of rising heat stress will only narrow down to half.

Published in the journal Geophysical Research Letters, the study – projecting the amount of heat stress residents of the region will experience in the future – finds with 2 degrees Celsius of warming, the population’s exposure to heat stress will nearly triple.  

Residents of South Asia already periodically experience heat waves at the current level of warming. Limiting warming to 1.5 degrees Celsius will likely reduce that impact by half, but deadly heat stress will become commonplace across South Asia.

As highlighted by the Weather Channel, a recent report from The Lancet Countdown on Health and Climate Change pointed out that India recorded over 31,000 heat-related mortality incidents in 2018 alone among the 65-plus aged population. This ranks India second, after China, which witnessed about 62,000 deaths in the same year. The study shows that people dwelling in major crop-producing Indian states of West Bengal, Uttar Pradesh and Punjab, along with residents of Sindh in Pakistan are most likely to face the brunt of the increasing number of heatwaves. Moreover, urban centres located on coastal belts, such as Kolkata, Mumbai and Hyderabad may also fall into the grip of heat stress.

With almost one quarter of the world’s population living in South Asia, the study underlines the urgency of addressing climate change. At present, the South Asian region, which also includes India, experiences periodic heatwaves, typically in the hot summer months between March and June. As per the World Meteorological Organization, a heatwave occurs when the daily maximum temperature crosses the average mark by 5°C or more consecutively for five days or more.

Earlier studies had projected that heatwaves would become more lethal by the end of the century. However, the authors of this study assert that this has already started to occur in South Asia, as the year 2015 already witnessed some of the most severe heat episodes on record. It is regarded as the fifth deadliest heatwave in history, which killed nearly 3500 people, out of which 2300 deaths were reported from India alone.

As described in the press release, earth has warmed by 1 degree Celsius since the start of the Industrial Revolution, according to the Intergovernmental Panel on Climate Change. On the current climate trajectory, it may reach 1.5 degrees Celsius of warming in 2040. This deadline leaves little time for South Asian countries to adapt. People living in South Asia are especially vulnerable to deadly heat waves because the area already experiences very hot, humid summers. Much of the population live in densely populated cities without regular access to air conditioning, and about 60% perform agricultural work and can’t escape the heat by staying indoors.

In the study, the researchers used climate simulations and projections of future population growth to estimate the number of people who will experience dangerous levels of heat stress in South Asia at warming levels of 1.5 and 2 degrees Celsius. They estimated the wet bulb temperature residents will experience, which is similar to the heat index, as it takes into account humidity as well as temperature. A wet bulb temperature of 32 degrees Celsius (89.6 degrees Fahrenheit) is considered to be the point when labour becomes unsafe, and 35 degrees Celsius (95 degrees Fahrenheit) is the limit to human survivability – when the body can no longer cool itself.

Their analysis suggests at 2 degrees of warming, the population’s exposure to unsafe labour temperatures will rise more than two-fold, and exposure to lethal temperatures rises 2.7 times, as compared to recent years.  

The results differ from a similar study conducted in 2017, which predicted that heat waves of lethal temperatures will occur in South Asia toward the end of the 21st century. The researchers suspect the earlier study is too conservative, as deadly heat waves have already hit the region in the past.

The study was supported by the National Climate Computing Research Center at the Oak Ridge National Laboratory, the Department of Energy and the National Oceanic and Atmospheric Administration.