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Thursday, July 1, 2021

'Wet-bulb' temperature ! .. a threshold hotter than the human body can withstand

Today a post on Pakistan – though it starts with Covid 19 – this is no post on the dreaded disease but something on Summer heat !!


Hundreds of desperate Pakistanis overwhelmed a government-run coronavirus vaccination centre in the capital on Monday as the nation grapples with a shortage of life-saving shots even as a decline in new infections has seen some restrictions eased. Most of those clamouring to be vaccinated were Pakistanis who work overseas — mainly in the Gulf Arab nations such as Saudi Arabia — who need a shot of the hard-to-find AstraZeneca vaccine to travel there. “We have a very limited capacity here, but for the past few days the centre has been overwhelmed by those wanting to travel abroad,” senior police official  told AFP.

Pakistan has so far fully or partially vaccinated nearly 12 million people from a population of 220 million, and mostly with the Chinese Sinopharm or Sinovac jabs. Most Gulf nations, however, require incoming foreign workers to be vaccinated with the AstraZeneca or Pfizer brands, which are in short supply in Pakistan.

Moving away, heard of ‘Jacobabad’ -  a city in Sindh, Pakistan, serving as both the capital city of Jacobabad District and the administrative center of Jacobabad Taluka,  the 43rd most populous city in Pakistan. The city itself is subdivided into eight Union Councils. Sitting very far away to the provincial boundaries of Sindh and Balochistan, Jacobabad became a city on the site of an existing village (Khangarh), and is crossed by the Pakistan Railway and many main roads of the province.

Often we hear from people, that temperatures are rising and it is hotter this year that it was before !  Chennaites are lucky – the  ‘agni natchathiram or katri’ this year passed off somewhat ordinarily without harming much in Chennai.   Not so, for many other parts of the Nation. Sad news is that the stifling heat has killed hundreds of people too.  Many parts of Andhra / Telengana experience ‘heat waves’.  During my stay in Kakinada, Wednesdays in Summer would be horrible – there would be 12 hours power cut – 8am to 8pm [there would be more unscheduled power cuts too] – as one returns from outside, one could feel the heat on the walls, in the water from taps and everywhere ! Places like Vijayawada would be hotter still !!

Those who love train travel and have travelled a lot -  would vouch - Travel by Grand Trunk Express from Delhi to Chennai would take 3 days (36 hours – if one starts on a Sat around 7 pm at Delhi – entire Sunday and would reach Chennai Central by 7 am on Monday).  By the time, train crosses Balharshah and Sirpur Kagaznagar – darkness would envelop and by Mancheral, one could experience the climate getting very hot .. .. it would peak at Ramagundam, then Warangal, Khammam and by midnight at Vijayawada, people would sweat in heat.

During peak summer – it would be torrid time for people of Andhra and Telengana as roads would melt in the heat.  Ramagundam, some 225 km from Hyderabad in Karimnagar district of Telangana, has always seen scorching summers. The city boasts of National Thermal Power Corporation’s 2,600 MW Ramagundam Super Thermal Power Station, the largest in South India. Besides, there are several open-cast coal mines run by the Singareni Collieries Company Limited.  On May 11, 2010, Ramagundam had recorded 49°Celsius, the highest in the last decade. 

Moving over to Pakistan, when  the full midsummer heat hits Jacobabad, the city retreats inside as if sheltering from attack. The streets are deserted and residents hunker down as best they can to weather temperatures that can top 52C (126F). Few have any air conditioning, and blackouts mean often there is no  electricity. The hospital fills with heatstroke cases from those whose livelihoods mean they must venture out.  Here is something excerpted from Telegraph UK. 


“When it gets that hot, you can't even stay on your feet,” explained one resident,  “It's a very, very difficult time when it goes beyond 50C. People do not come out of their houses and the streets are deserted,”  a shopkeeper, adds. This city of some 200,000 in Pakistan's Sindh province has long been renowned for its fierce heat, but recent research has conferred an unwelcome scientific distinction.  Its mixture of heat and humidity has made it one of only two places on earth to have now officially passed, albeit briefly, a threshold hotter than the human body can withstand.  With this region of Pakistan along the Indus Valley considered one of the places most vulnerable to climate change in the world, there are fears that Jacobabad's temperatures may increase further, or other cities may join the club.

“The Indus Valley is arguably close to being the number one spot worldwide,” says Tom Matthews, a lecturer in climate science at Loughborough University. “When you look at some of the things to worry about, from water security to extreme heat, it's really the epicentre.” Mr Matthews and colleagues last year analysed global weather station data and found that Jacobabad and Ras al Khaimah, north east of Dubai in the United Arab Emirates, have both temporarily crossed the deadly threshold. The milestone had been surpassed decades ahead of predictions from climate change models. The researchers examined what are called wet bulb temperatures. These are taken from a thermometer covered in a water-soaked cloth so they take into account both heat and humidity.  Wet bulb thermometer readings are significantly lower than the more familiar dry bulb readings, which do not take humidity into account. Researchers say that at a wet bulb reading of 35C, the body can no longer cool itself by sweating and such a temperature can be fatal in a few hours, even to the fittest people. 

 “It approximates how warm it feels to humans because we cool via sweating,” Mr Matthews says. “We rely on that exclusively. When you use that measure, the wet bulb temperature, the two regions that stand out on earth are the shores of the Gulf and the Indus Valley in Pakistan. They are truly exceptional.”  Jacobabad crossed the 35C wet bulb threshold in July 1987, then again in June 2005, June 2010 and July 2012. Each time the boundary may have been breached for only a few hours, but a three-day average temperature has been recorded hovering around 34C in June 2010, June 2001 and July 2012. The dry bulb temperature is often over 50C in the summer.

Patchy death records mean it is not clear whether the crossing of the threshold resulted in a wave of fatalities. The effects of entering the danger zone are likely to be blurred, for example with cooler interiors of buildings temporarily sheltering residents from the worst. It also depends on how long the threshold is crossed. Jacobabad and Ras al Khaimah may share fierce temperatures, but they are otherwise very different and illustrate the different challenges that places will face under climate change. In the wealthy UAE, where electricity and air conditioning are plentiful, the threshold may have little effect on residents. In Jacobabad, where many subsist on wages of only a couple of pounds a day, residents must find other ways to adapt. Jacobabad's crown for unsurvivable temperatures may conjure pictures of Death Valley-like deserts, but it is an agricultural hub fed by irrigation canals.  Stretches of the town's bazaar are dedicated to keeping cool. Shops sell electric fans and low-tech washing machine-sized coolers that emit a refreshing mist. Electric solutions are undermined by frequent power cuts however. In the city centre, residents often lose power for three or four hours, while in more distant areas the gaps are longer.



The solution for some is a solar panel, though at £36 each they are expensive for many. Cheap Chinese batteries are also available. “Everyone needs electricity here. It's not for television, it's for keeping cool,” says one electrical goods trader.  Ice is also popular, with factories making huge blocks which are then hacked into 10p chunks at roadside stalls. When all else fails, there are hand fans and people also simply dunk buckets of water over their heads. For those who can afford it, there is the chance to spend the summer in Quetta or Karachi, which are still fiercely hot, but offer some relief. Most stay.

“The people are used to it, they have developed a resistance,” shrugs one administration official. People also said the heat was only one of many problems they faced. Price hikes have caused economic devastation, while there is a lack of fresh drinking water and the city's supplies are brackish. 

High temperatures have also recently made headlines in the US, where Portland, Oregon, hit an all-time local high of 42C (108F) on a dry bulb scale.  As temperatures rise and rainfall patterns shift, difficulties with farming, irrigation, disease and labour are predicted by 2050 to badly hit people's quality of living in many parts of the World, especially for poor people.

With regards – S. Sampathkumar
29th June 2021 

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