Without action, climate change could devastate South Asia, says MIT study
Washington (ISJ) - Climate change could lead to summer heat waves with levels of heat and humidity that exceed what humans can survive without protection in South Asia, warned a new study. There is still time to avert such severe warming if measures are implemented now to reduce the dire consequences of global warming.
Without significant reductions in carbon emissions, the study shows these deadly heat waves could begin within as little as a few decades to strike India, Pakistan, and Bangladesh, including the fertile Indus and Ganges river basins that produce much of the region's food supply.
The new findings, based on detailed computer simulations using the best available global circulation models, were described by a team of researchers in the latest edition of the journal Science Advances.
The study follows an earlier report by Elfatih Eltahir, Professor of Civil and Environmental Engineering at MIT and his team that looked at projected heat waves in the Persian Gulf region. While the number of extreme-heat days projected for that region was even worse than for South Asia, Eltahir said the impact in the latter area could be vastly more severe.
The Persian Gulf area has a relatively small, relatively wealthy population and little agricultural land, the areas likely to be hardest hit in northern India, Bangladesh, and southern Pakistan are home to 1.5 billion people. These areas are also 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.
"That makes them very vulnerable to these climatic changes, assuming no mitigation," said Eltahir.
Map showing the maximum wet-bulb temperatures (temperature+humidity) reached in this region since 1979
While the projections show the Persian Gulf may become the region of the worst heat waves on the planet, northern India is a close second, Eltahir said, and eastern China, also densely populated, is third. But the highest concentrations of heat in the Persian Gulf would be out over the waters of the Gulf itself, with lesser levels over inhabited land.
The new analysis is based on recent research showing that hot weather's most deadly effects for humans comes from a combination of high temperature and high humidity, an index which is measured by a reading known as wet-bulb temperature. This reflects the ability of moisture to evaporate, which is the mechanism required for the human body to maintain its internal temperature through the evaporation of sweat. At a wet-bulb temperature of 35 degrees Celsius (95 degrees Fahrenheit), the human body cannot cool itself enough to survive more than a few hours.
A previous study of temperature and humidity records showed that in today's climate, wet-bulb temperatures have rarely exceeded about 31 C anywhere on Earth. While the earlier report from Eltahir and his colleagues showed that this survivability limit would start to be exceeded occasionally in the Persian Gulf region by the end of this century, actual readings there in the summer of 2015 showed that the 35-degree wet-bulb limit had almost been reached already, suggesting that such extremes could begin happening earlier than projected. The summer of 2015 also produced one of the deadliest heat waves in history in South Asia, killing an estimated 3,500 people in Pakistan and India.
And yet, India and China remain two countries where emission rates of greenhouse gases continue to rise, driven mostly by economic growth, Eltahir remarked.
"So I think these results pose a dilemma for countries like India. Global warming is not just a global problem — for them, they will have some of the hottest spots," said Eltahir. "With the disruption to the agricultural production, it doesn't need to be the heat wave itself that kills people. Production will go down, so potentially everyone will suffer."
A separate study by researchers at the University of California at Irvine and elsewhere, published recently also in Scientific Advances, reached similar conclusions based on a different kind of analysis using recent weather records.
But while the study provides a grim warning about what could happen, it is far from inevitable, Eltahir stressed. The study examined not just the "business as usual" case but also the effects under a moderate mitigation scenario, which showed that these dramatic, deadly effects can still be averted. "There is value in mitigation, as far as public health and reducing heat waves," he said. "With mitigation, we hope we will be able to avoid these severe projections. This is not something that is unavoidable."
"This study provides vitally important information for planning for a hot, wet future in South Asia," said Matthew Huber, a professor of earth, atmospheric, and planetary sciences at Purdue University, who was not involved in this research "The results are impressive and, frankly, oppressive," he added. "The study shows that unfettered warming is likely to do substantial harm to the health and well-being of the most populous democracy on Earth. This is very bad news."
Image courtesy: MIT
Link to the original study: http://advances.sciencemag.org/content/3/8/e1603322