If global warming continues, a new report suggests, natural human cooling through sweat may lose its effectiveness as the environment exceeds the temperature of the human body.
An analysis of possible human adaptability to climate change by Tom Vanderbilt published this week in Medium states that savanna areas where evolutionary changes were said to have taken place were hot, “but not necessarily the wet-bulb hellscapes that some climate change models are projecting.”
When speaking of climate change impacts, many “focus on sea-level rise and how coastal dwellers will adapt,” Vanderbilt observes, while in reality “heat may be the bigger story.”
Citing climate scientists Steven Sherwood and Matthew Huber, Vanderbilt says that “if warmings of 10 degrees Celsius were really to occur in next three centuries, the area of land likely rendered uninhabitable by heat stress would dwarf that affected by rising sea level.”
In this regard, heat stress “deserves more attention as a climate change impact,” he says, especially because it will have a direct impact upon the human body.
Once a certain threshold is reached, “we can no longer cool ourselves by convection or evaporation. Our environment becomes, in effect, a steam room; sweating, our great adaptive tool, is no longer effective,” Vanderbilt warns.
Thus, if global warming predictions hold true, he says, the body’s capability for self-cooling in extreme heat may prove insufficient for new environmental scenarios.
The author says that certain studies have indicated that the “critical thermal maximum” for human beings is 35 degrees Celsius (95º F), or around skin temperature. Beyond this temperature, “any exposure for more than six hours would probably be intolerable even for the fittest of humans, resulting in hyperthermia,” or heatstroke, Vanderbilt says, citing a 2015 article by Jeremy Pal and Elfatih Eltahir in Nature Climate Change.
According to Pal and Eltahir, thanks to climate change “the deadly 35-degree threshold will increasingly be reached by the end of the century, in regions like the Persian Gulf and the densely inhabited regions around the Indus and Ganges river basins.”
And “as temperatures continue to climb and indoor air-conditioning systems are strained, some adaptive responses will begin to kick in,” Vanderbilt predicts, which could include an alteration in human organs, an evolution of human sweat “better suited for aridity,” a permanent shift in metabolism, or even becoming taller and longer limbed “so as to dissipate heat more reliably.”
Then again, one supposes that if current climate models turned out to be correct, while certain parts of the earth slowly entered a danger zone of higher temperatures, other parts of the planet would logically mutate from uninhabitable frozen wasteland into territory friendlier to human dwelling and agriculture.
When dealing with climate forecasts for 50 or 100 years in the future, the numbers are only as reliable as the models that generate them.
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