South Asia may face killer hu­mid­ity boosted by warm­ing

30% of the pop­u­la­tion here could be ex­posed to deadly heat waves

Muscat Daily - - FRONT PAGE - Matt Mc­Grath

Mil­lions of peo­ple liv­ing in South Asia face a deadly threat from heat and hu­mid­ity driven by global warm­ing, ac­cord­ing to a new study

Mil­lions of peo­ple liv­ing in South Asia face a deadly threat from heat and hu­mid­ity driven by global warm­ing, ac­cord­ing to a new study.

Most of In­dia, Pak­istan and Bangladesh will ex­pe­ri­ence tem­per­a­tures close to the lim­its of sur­viv­abil­ity by 2100, with­out emis­sions re­duc­tions. The re­search says the frac­tion of the pop­u­la­tion ex­posed to dan­ger­ous, hu­mid heat waves may reach 30 per cent.

Wet bulb threat

Most of­fi­cial weather sta­tions around the world mea­sure tem­per­a­ture with two ther­mome­ters. The first, or ‘dry bulb’ in­stru­ment, records the tem­per­a­ture of the air. The other, or ‘wet bulb’ ther­mome­ter, mea­sures rel­a­tive hu­mid­ity in the air and the re­sults are nor­mally lower than just the pure air tem­per­a­ture.

For hu­mans, this wet bulb read­ing is crit­i­cally im­por­tant.

While the nor­mal tem­per­a­ture in­side our bod­ies is 37°C, our skin is usu­ally at 35°C. This tem­per­a­ture dif­fer­ence al­lows us to dis­si­pate our own meta­bolic heat by sweat­ing.

How­ever, if wet bulb tem­per­a­tures in our en­vi­ron­ment are at 35°C or greater, our abil­ity to lose heat de­clines rapidly and even the fittest of peo­ple would die in around six hours.

While a wet bulb 35°C is con­sid­ered the up­per limit of hu­man sur­viv­abil­ity, even a hu­mid tem­per­a­ture of 31°C is con­sid­ered an ex­tremely dan­ger­ous level for most peo­ple.

Recorded wet bulb tem­pera-

tures on Earth have rarely ex­ceeded 31°C. How­ever, in 2015 in Iran, me­te­o­rol­o­gists saw wet bulb tem­per­a­tures very close to 35°C. In the same sum­mer, a deadly heat­wave killed 3,500 peo­ple in In­dia and Pak­istan.

The re­searchers in­volved came to their con­clu­sions by us­ing a high res­o­lu­tion cli­mate model, that was tested against ob­ser­va­tions.

They pro­jected wet bulb tem­per­a­tures to the end of this cen­tury us­ing two dif­fer­ent cli­mate change sce­nar­ios.

When the model ex­am­ined a high emis­sions fu­ture, the wet bulb tem­per­a­ture would ap­proach the 35°C thresh­old ‘over most of South Asia, in­clud­ing the Ganges river val­ley, north east­ern In­dia, Bangladesh, the east­ern coast of China, north­ern Sri Lanka and the In­dus val­ley of Pak­istan’.

Ac­cord­ing to the sci­en­tists, around 30 per cent of the pop­u­la­tion is pro­jected to live in a cli­mate char­ac­terised by a me­dian of the max­i­mum an­nual wet bulb tem­per­a­ture of 31°C or more.

At present, the num­ber of peo­ple fac­ing this level of threat is es­sen­tially zero.

“The val­leys of the In­dus and the Ganges rivers are where the wa­ter is, they’re where the agri­cul­ture is and they’re where the pop­u­la­tion has ex­ploded,” au­thor Pro­fes­sor El­fatih El­tahir from the

Mas­sachusetts In­sti­tute of Tech­nol­ogy (MIT) told BBC News.

“Our map that shows where the tem­per­a­ture ex­tremes are, it’s the same place that you have rel­a­tively poor peo­ple who pre­dom­i­nantly have to work in agri­cul­ture and there are so many that they hap­pen to co­in­cide in a re­gion where the haz­ard is max­imised.”

Im­pacts of Paris

If the rise in global tem­per­a­tures is con­tained to just over two de­grees, roughly in line with the Paris Cli­mate Agree­ment, the frac­tion of the pop­u­la­tion ex­posed to hu­mid heat above 31°C drops to two per cent.

Heat­waves up to and be­yond 31°C are pro­jected to be­come much more fre­quent if lit­tle ac­tion is taken on cut­ting car­bon. In most lo­ca­tions, the once-every-25-year heat­wave in the present cli­mate is pro­jected to be­come an ap­prox­i­mately on­cea-year oc­cur­rence. If the lim­i­ta­tions agreed in Paris are met, these heat­waves are likely to hap­pen every two years.

“Cli­mate change doesn’t look like an ab­stract con­cept if you look at In­dia,” said Pro­fes­sor El­tahir.

“This is some­thing that is go­ing to im­pact your most vul­ner­a­ble pop­u­la­tion in ways that are po­ten­tially pretty lethal. But it is avoid­able, it is pre­ventable.”

Other re­searchers say the ‘dam­ag­ing and down­right deadly’ con­di­tions de­scribed in this study are likely to oc­cur if the world doesn’t em­brace rapid and sub­stan­tial cuts in car­bon emis­sions.

“Ei­ther we - the whole world - de­cide to re­duce car­bon emis­sions sub­stan­tially or we face a highly dan­ger­ous sce­nario in one of the most pop­u­lous re­gions in the world, with a deep his­tory and cul­ture, and also a his­tory of po­lit­i­cal in­sta­bil­ity,” said Pro­fes­sor Matthew Hu­ber from Pur­due Univer­sity, US, who wasn't part of the re­search team.

Ac­cord­ing to Pro­fes­sor Christoph Schaer from the In­sti­tute of At­mo­spheric and Cli­mate Science at ETH Zurich, the work is ‘alarm­ing’.

“The study is cred­i­ble as ex­tremely hot and hu­mid heat waves al­ready oc­cur un­der cur­rent cli­matic con­di­tions in some of the ar­eas con­sid­ered,” he said.

“As con­di­tions are close to a crit­i­cal health thresh­old al­ready to­day, a warm­ing of a few de­grees could strongly in­crease the risk of deadly heat­waves.”

Ei­ther we de­cide to re­duce car­bon emis­sions or face a highly dan­ger­ous sce­nario

Prof Matthew Hu­ber


Sci­en­tists say most of In­dia, Pak­istan and Bangladesh will ex­pe­ri­ence tem­per­a­tures close to sur­viv­abil­ity lim­its by 2100 if car­bon emis­sions are not checked


Monks from the Bharat Sevashram Sangha, an In­dian so­cio-re­li­gious body, use a boat to bring food do­na­tions to flood-af­fected vil­lagers around Uday­narayan­pur, some 83km west of Kolkata, on Au­gust 1

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