Increasing fatal combination of heat and humidity – avoid it as much as you can during summer holidays!!

sweltering heat.

In this era of global warming, the weather patterns across the regions in  many continents have become unpredictable. The recent impact of Covid-19 virus on the global community and the present struggle to contain its  spread  are a matter of great concern for the medical community on one hand,  and on the other, there has been considerable reduction in CO 2 concentration in the atmosphere. Even if the corona virus pandemic soon comes to an end, the problem of global warming will haunt us.  In the tropics and subtropics, the combined effect of heat and humidity on the human body is a serious issue. Humidity is not necessarily related to heat – it is to do with how much water vapor is in the air. It is not advisable to stay outdoors for a long time. Elderly people and children should avoid as much as they can. 

Tackling heat and humidity.

In the tropics and subtropics humidity plays a vital role and as we know that  ”humid heat” is  tougher to deal with  than the “dry” kind. Scientists  predict that in the ensuing mid century  in the tropical and subtropical regions the combined effect of humidity and heat in the warming climate will reach higher levels that we ever experienced before.  At stake will be the physiological limits of human survival combined with falling  economies.The study on ”heat and humidity”  appears this week May, 2020 in the journal Science Advances.

However,  the new research work says that such climatic conditions have already shown up. In many places in Africa, Asia, USA,  US Gulf  Coast,  South America, etc  there are  thousands of previously rare or unprecedented bouts of extreme heat and humidity.  The scientists spotted more than a dozen recent brief outbreaks surpassing the theoretical human ‘survival limit’ along the Persian Gulf.  Such outbreaks may be localized and short-lived,  just hours.  But the main worry is their increasing frequency and intensity. 

Avoid extreme heat.

The lead author Colin Raymond, who did the study  as a PhD. student at Columbia University’s Lamont-Doherty Earth Observatory says,  “Previous studies projected that this would happen several decades from now, but this shows it’s happening right now. The duration of the event and the affected area ”will  grow in direct correlation with global warming.”

From the  weather stations  data  during the period 1979 to 2017, the authors  inferred that the combined  extreme heat/humidity factors  doubled over the study period. Places like  India, Bangladesh, Pakistan,  northwestern Australia,  along the coasts of the Red Sea and Mexico’s Gulf of California experienced repeated incidents.  The highest, potentially fatal, readings, were noted down 14 times in the cities of  many Arab countries in particular, Saudi Arabia, Qatar, United Arab Emirates etc. This study identified some cities and hot spots in SE USA, particularly, the Gulf Coast in east Texas,  the Florida Panhandle,  Louisiana etc. Such conditions did prevail in the interior land as back as  Arkansas and along the southeastern coastal plain.

One interesting fact emerging  out from this interesting study is that  the incidents tend to occur in cluster  on coastlines along confined seas, gulfs and straits. Part of the reason is  ‘evaporating seawater’ supplies  abundant moisture to be sucked up by hot air. In some areas further inland, moisture-laden monsoon winds prevail. Earlier climate studies  focussed more on large areas and over several hours when measuring  average  heat and humidity  at a time.  In the present study, the author and his team gathered hourly data from 7,877 individual weather stations to look at the real situation in small places not covered before. This detailed data helped them pinpoint  shorter-lived bouts affecting smaller areas.

The crux of  the problems faced by the humans is we cool  our bodies by sweating; water expelled through the skin removes excess body heat, and when it evaporates, it carries that heat away.  But,  humidity worsens the effects of heat.  Air already
 laden with moisture  has to take more. The evaporation of sweat slows down,  in some case it stops. Now the body has to manage enormous heat far beyond the tolerance level. A physically 
fit man with bare body right below the shadow of a tree  can 
face danger in a situation like this with  unlimited access to drinking. 
Earlier research  suggested that strong well-adopted people  can not engage in  normal outdoor activities when the wet bulb (“heat index”;  heat/humidity effect used by the US) hits 32 C, equivalent to a heat index of 132 F. People will fall down like nine pins in such a condition. A reading of 35 —  as reported in the Persian Gulf cities, is  theoretically the maximum  survival limit – a heat index of 160 F. (The heat index actually ends at 127 F).  The study found that  since 1979,  worldwide, wet-bulb readings approaching or exceeding 30C  have doubled. Readings of 31 — previously believed to occur only rarely — totaled around 1,000. Readings of 33 — previously thought to be almost nonexistent — totaled around 80.
In the past in July in  the US the heat wave touched  30 degree  C on the wet bulb ( heat indexes approaching 115 F  and more in places). This caused  many deaths.  Heat-related problems are on the increase  resulted in many deaths.   Between 2008 and 2018 heat stroke or heat exhaustion  affected many army men on the domestic bases and registered 60% growth over that period. Main reason:  high-humidity heat waves and muggy weather condition. In Europe and Russia, it caused a big casualty.  The highest heat/humidity events may impact the farm economy  and commerce if people are forced to stay indoors in A/C rooms to avoid heat wave.

avoid hot outdoor

Increasing heat and humidity in the future would spell doom to many countries including the US. The communities world over are close to the limit of tolerance. Concerted efforts must be made by the countries to reduce the global warming over a specified time from now. The wet-bulb readings should come down to a comfortable level for people to stay outdoors without getting

affected by heat/humidity factors.

(The study was coauthored by Tom Matthews, a lecturer in climate science at Lough borough University in the United Kingdom. Colin Raymond is now a postdoctoral researcher at NASA’s Jet Propulsion Laboratory)
Journal Reference:
Colin Raymond, Tom Matthews, Radley M. Horton. The emergence of heat and humidity too severe for human tolerance. Science Advances, 2020; 6 (19): eaaw1838 DOI: 10.1126/sciadv.aaw1838

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