Deadly heat waves will be common in South Asia, even at 1.5 degrees of warming
People living in South Asia already experience potentially deadly heat waves, but these events will likely become more commonplace in the coming decades even if global warming is limited to the 1.5 degrees Celsius (2.7 degrees Fahrenheit) target from the Paris Agreement, according to new research.
WASHINGTON—Residents of South Asia already periodically experience heat waves at the current level of warming. But a new 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.
Limiting warming to 1.5 degrees Celsius will likely reduce that impact by half, but deadly heat stress will become commonplace across South Asia, according to the new study in Geophysical Research Letters, AGU’s journal publishing high-impact, short-format reports with immediate implications spanning all Earth and space sciences.
With almost one quarter of the world’s population living in South Asia, the new study underlines the urgency of addressing climate change.
“The future looks bad for South Asia, but the worst can be avoided by containing warming to as low as possible,” said Moetasim Ashfaq, a computational climate scientist at Oak Ridge National Laboratory and corresponding author of the new study. “The need for adaptation over South Asia is today, not in the future. It’s not a choice anymore.”
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. “Only half a degree increase from today is going to cause a widespread increase in these events,” Ashfaq said.
A hot region getting hotter
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 new 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 labor 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 labor temperatures will rise more than two-fold, and exposure to lethal temperatures rises 2.7 times, as compared to recent years.