Deadly heat waves could hit South Asia this century: study

August 2, 2017
Credit: CC0 Public Domain

In South Asia, a region of deep poverty where one-fifth of the world's people live, new research suggests that by the end of this century climate change could lead to summer heat waves with levels of heat and humidity that exceed what humans can survive without protection.

There is still time to avert such severe warming if measures are implemented now to reduce the most dire consequences of global warming. However, under business-as-usual scenarios, without significant reductions in carbon emissions, the study shows these deadly could begin within as little as a few decades to strike regions of 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, are described this week in the journal Science Advances, in a paper by MIT professor of environmental engineering Elfatih Eltahir, MIT Research Scientist Eun Soon Im, and Professor Jeremy Pal at Loyola Marymount University in Los Angeles.

The study follows an earlier report by Eltahir and his team that looked at projected 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 says the impact in the latter area could be vastly more severe. That's because while 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 labor out in the open and unprotected from the sun.

"That makes them very vulnerable to these climatic changes, assuming no mitigation," says Eltahir, who spoke with MIT News from Singapore, where he is carrying out follow-up research on potential climate effects in that area.

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 says, 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 show 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 says. "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" on the planet. In fact, 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.

That paper was "complementary to ours, which is based on modeling," Eltahir says. The new analysis looked at results from three of the more than 20 comprehensive global climate models, which were selected because they most accurately matched actual weather data from the South Asian region. The study shows that by century's end, absent serious reductions in global emissions, the most extreme, once-in-25-years heat waves would increase from wet-bulb temperatures of about 31 C to 34.2 C. "It brings us close to the threshold" of survivability, he says, and "anything in the 30s is very severe."

In today's climate, about 2 percent of the Indian population sometimes gets exposed to extremes of 32-degree wet-bulb temperatures. According to this study, by 2100 that will increase to about 70 percent of the population, and about 2 percent of the people will sometimes be exposed to the survivability limit of 35 degrees. And because the region is important agriculturally, it's not just those directly affected by the heat who will suffer, Eltahir says: "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."

But while the study provides a grim warning about what could happen, it is far from inevitable, Eltahir stresses. 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 says. "With mitigation, we hope we will be able to avoid these severe projections. This is not something that is unavoidable."

Explore further: An intolerable unimaginable heat forecast for Persian Gulf

More information: E.-S. Im at Hong Kong University of Science and Technology in Hong Kong, China el al., "Deadly heat waves projected in the densely populated agricultural regions of South Asia," Science Advances (2017). advances.sciencemag.org/content/3/8/e1603322

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18 comments

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Porgie
1 / 5 (9) Aug 02, 2017
Yes and maybe not HAHAHAHAHHAH What BS!!!!
howhot3
5 / 5 (7) Aug 02, 2017
It's the Soylent Green scenario where temperatures become so high from global warming that agriculture is devastated and the planet's populations starve. Of course, that means food riots, wars and mass migrations and resettlements (assuming that the wars don't go nuclear). So we really do need to stop climate change immediately.

But of course there are political realities that Republicans want us all to face, like avoiding taxes, making sure that industries get a free ride, make sure that oil, coal and gas are subsidised for ever. Oh and they want to keep people stupid too! So ignore science, education, training and development and put more money helping barons of religiosity and fiction. Conservatism will destroy this mankind one small cut at a time.

howhot3
5 / 5 (6) Aug 02, 2017
For those complete right-wing denier flakes and nuts that want to claim 'BS' on mankind's most certain fate, here is a site I like to visit and watch in realtime.

https://earth.nul...1,39.703

Just toggle it to temp was well as CO2sc. Fun.
Shootist
1 / 5 (8) Aug 03, 2017
Climate change as presented in the media, and seemingly as supported by Government, is a fraud of the first order. These people have no honor.

Australia's Bureau of Meteorology (BOM) has been caught red handed erasing record-breaking cold temperatures from its data records. http://www.breitb...ratures/
TheGhostofOtto1923
1 / 5 (1) Aug 03, 2017
Of course, that means food riots, wars and mass migrations and resettlements
-But these things have already been taking place at unprecedented levels and AGW is not the culprit- it's overpopulation. IOW the human tropical reproductive rate coupled with the religionist mandate to outgrow and overwhelm the competition.

The people who are trying to convince you that the problem can be solved in a few decades are the same ones who are counting on AGW to solve the real problem by destroying these obsolete cultures where they reside, in a few decades.

Either way, no matter what you do, temps will continue to rise and these cultures will be destroyed as a result. And as always only the best and brightest and most ambitious of the people there will decide to save themselves and their families, and head north, while the rest will choose to sit and pray to their gods for salvation... and die.
TheGhostofOtto1923
1 / 5 (1) Aug 03, 2017
It's the Soylent Green scenario where temperatures become so high from global warming that agriculture is devastated and the planet's populations starve
Soylent green was about overpopulation, not AGW. You missed the whole point of the movie. So many people they had to shovel them up and turn them into food.
https://youtu.be/-wa4U6TQlNI

-No short sleeves or shorts in the entire crowd-
Anonym
1 / 5 (1) Aug 03, 2017
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.

Ah, "science." Has any healthy individual ever actually died after a couple hours' exposure to 95 degrees F? LOL. Billions of people somehow survive the experience, every single day. In my neck of the woods, the "average" high temp in early August is 98F, so clearly, there should be bodies piled high at every bus stop.

I expect the article's writer hasn't broken a sweat very often.

btw, the "wet-bulb temp," aka the "heat index," does not take into account cooling caused by heat advection (by the wind). It's a lab exercise with no real-world relevance, except to make people feel hotter. Which is the point, isn't it?

gkam
2 / 5 (4) Aug 03, 2017
"Soylent green was about overpopulation, not AGW. You missed the whole point of the movie."

No, YOU missed the point. The oceans were dying because corporations killed the environment, our life-support system.

No trees, no food.
TheGhostofOtto1923
2.3 / 5 (3) Aug 03, 2017
"Soylent green was about overpopulation, not AGW. You missed the whole point of the movie."

No, YOU missed the point. The oceans were dying because corporations killed the environment, our life-support system.

No trees, no food.
Hi there little psychopath, back from the dead? Posting in your jammies now eh?
gkam
2.6 / 5 (5) Aug 03, 2017
Shootist refers to a right-wing political nutjob site for science!

It is "Conservative Science".
Turgent
1 / 5 (1) Aug 03, 2017
"Projection" paper reads like an academic exercise. "According to the global historical reanalysis [temperature] for modern record (1979–2015)" Change the historical record to fit the prediction. "reanalysis" precious.
Turgent
1 / 5 (2) Aug 03, 2017
Should also have noted. Paper did not say whether it was the 1st 2nd 3rd or 7th reanalysis. Basically current temperature recording is incompatible with past or the folks recording the low temperatures were liars.

"Who controls the past controls the future. Who controls the present controls the past." George Orwell from his book 1984
mtnphot
5 / 5 (3) Aug 03, 2017
Climate change as presented in the media, and seemingly as supported by Government, is a fraud of the first order. These people have no honor.

Australia's Bureau of Meteorology (BOM) has been caught red handed erasing record-breaking cold temperatures from its data records. http://www.breitb...ratures/


Breitbart is such a reputable source of news. Slightly less accurate than the Onion.
Captain Stumpy
4 / 5 (4) Aug 05, 2017
@mtnphot
Breitbart is such a reputable source of news. Slightly less accurate than the Onion.
ROTFLMFAO
...and nowhere near as funny
howhot3
5 / 5 (1) Aug 07, 2017
@Ghost, I think you are right about "Soylent Green" being about over population. But I think they also mention Global Warming as a cause. This was a sci-fi film made before science was politicised. Now that science is politicised I have to laugh at all of the idiots that deny the sciences just to support some screwed up political position. Especially when those sciences are all 99% in agreement of the dangers global warming puts on the whole planet.

howhot3
5 / 5 (1) Aug 07, 2017
Here is the green-house effect mentioned in Soylent Green... Enjoy your crow..

https://www.youtu...7yZ9kG9A
barakn
not rated yet Sep 20, 2017
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.

Ah, "science." Has any healthy individual ever actually died after a couple hours' exposure to 95 degrees F? LOL. Billions of people somehow survive the experience, every single day. In my neck of the woods, the "average" high temp in early August is 98F, so clearly, there should be bodies piled high at every bus stop. -Anonym
Here Anonym appears to confuse wet-bulb temperature with actual temperature. The two wouldn't be the same unless the relative humidity was at 100%, i.e. the dew point was also 95° F. Coincidentally, 95° F is the world record dew point, reached at Dhahran, Saudi Arabia, at 15:00 AST on July 8, 2003. The dry-bulb temperature was 108° F. https://www.wunde...res.html
barakn
5 / 5 (1) Sep 20, 2017
btw, the "wet-bulb temp," aka the "heat index," does not take into account cooling caused by heat advection (by the wind). It's a lab exercise with no real-world relevance, except to make people feel hotter. Which is the point, isn't it?
Suddenly Anonym appears to notice the word "wet-bulb," but then confuses it with heat index. Using the Dhahran event mentioned above, the wet-bulb temp was 95° F, but the heat index was176° F.

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