|sweltering heat. smwac.net|
|Tackling heat and humidity. wanderwisdom.com|
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. manchesterinklink.com|
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.
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(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)
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