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There's an upper limit to human survivability given heat and humidity levels: Wet Bulb temperature of 35C. Humans can't sweat fast enough to maintain homeostas

There's an upper limit to human survivability given heat and humidity levels: Wet Bulb temperature of 35C. Humans can't sweat fast enough to maintain homeostasis. https://www.weather.gov/safety/heat-index https://www.weather.gov/safety/heat-index Hasn't happened yet for sufficient periods in any substantially populated impoverished area, but when it does, well, the horror will be incalculable.

scruple 6y ago
Is the wet bulb temperature the same for all humans or does age/size come into play?
- splitrocket 6y ago
  Well, interestingly enough, the factors are both what you would normally consider a "vulnerable" population, but also, folks with a high metabolic rate (athletes) as well. https://ksi.uconn.edu/emergency-conditions/heat-illnesses/exertional-heat-stroke/heat-stroke-risk-factors/ https://ksi.uconn.edu/emergency-conditions/heat-illnesses/ex... Low hydration is also a factor, and when you consider than millions of USA-ians may not be able to afford their water bill, well... https://www.consumerreports.org/personal-finance/millions-of-americans-cant-afford-water-as-bills-rise-80-percent-in-a-decade/ https://www.consumerreports.org/personal-finance/millions-of...
- hannob 6y ago
  The wet bulb temperature is when your body can no longer cool with sweat. This is the same for everyone and is a relation between humidity and temperature. This is basically a physical thing and is the same for everyone. It means your body temperature will just go up until it reaches a point where you can no longer survive. Of course there's still differences on how much that matters. A healthy person can sustain a longer period of time with a slightly elevated temperature. A person with health problems may have issues much earlier. But in the end... with wet bulb temperature noone can survive without external cooling for longer periods of time.
czbond 6y ago
I don't disagree - but the south of USA this is just called "August"
- roter 6y ago
  It is hot & humid but likely not exceeding 35C. There are figures in [0] that show the 99.9% wet bulb typically is in the range 27-29C for the south eastern US. The "hot" spots are in the UAE, Iran, etc. Being close to very hot body of water does not help. [0] https://advances.sciencemag.org/content/6/19/eaaw1838 https://advances.sciencemag.org/content/6/19/eaaw1838
- raiyu 6y ago
  I moved from nyc to Miami and actually find the opposite. After three years here there was only one year worse than being in nyc during the summer. The summer almost feels milder here. Anecdotally of course.
- magicalhippo 6y ago
  It might be >35C as read on a regular thermometer in August in the south of US. However the wet-bulb temperature[1] is, as the name implies, the temperature a thermometer covered in water-soaked cloth. If the water evaporates, it will cool the thermometer down, and as such will read less than a regular (dry-bulb) thermometer. For example, if the dry-bulb temperature is 35C and the relative humidity is 75%, then the wet-bulb temperature would be about 31C[3]. This means the body can still evaporate sweat to cool down, albeit not by much. If you got both a wet-bulb and a dry-bulb thermometer side by side, you can use it to calculate the relative humidity[2]. [1]: https://en.wikipedia.org/wiki/Wet-bulb_temperature https://en.wikipedia.org/wiki/Wet-bulb_temperature [2]: https://en.wikipedia.org/wiki/Hygrometer#Psychrometer_(wet-and-dry-bulb_thermometer) https://en.wikipedia.org/wiki/Hygrometer#Psychrometer_(wet-a... [3]: https://www.psychrometric-calculator.com/HumidAirWeb.aspx https://www.psychrometric-calculator.com/HumidAirWeb.aspx
omosubi 6y ago
I can't find a link right now but I read somewhere that farmers in Costa Rica were starting to get liver damage because the wet bulb temperature had been reached there so we're starting to see the effects already

scruple 6y ago

Is the wet bulb temperature the same for all humans or does age/size come into play?

splitrocket 6y ago
Well, interestingly enough, the factors are both what you would normally consider a "vulnerable" population, but also, folks with a high metabolic rate (athletes) as well. https://ksi.uconn.edu/emergency-conditions/heat-illnesses/exertional-heat-stroke/heat-stroke-risk-factors/ https://ksi.uconn.edu/emergency-conditions/heat-illnesses/ex... Low hydration is also a factor, and when you consider than millions of USA-ians may not be able to afford their water bill, well... https://www.consumerreports.org/personal-finance/millions-of-americans-cant-afford-water-as-bills-rise-80-percent-in-a-decade/ https://www.consumerreports.org/personal-finance/millions-of...
hannob 6y ago
The wet bulb temperature is when your body can no longer cool with sweat. This is the same for everyone and is a relation between humidity and temperature. This is basically a physical thing and is the same for everyone. It means your body temperature will just go up until it reaches a point where you can no longer survive. Of course there's still differences on how much that matters. A healthy person can sustain a longer period of time with a slightly elevated temperature. A person with health problems may have issues much earlier. But in the end... with wet bulb temperature noone can survive without external cooling for longer periods of time.

czbond 6y ago

I don't disagree - but the south of USA this is just called "August"

roter 6y ago
It is hot & humid but likely not exceeding 35C. There are figures in [0] that show the 99.9% wet bulb typically is in the range 27-29C for the south eastern US. The "hot" spots are in the UAE, Iran, etc. Being close to very hot body of water does not help. [0] https://advances.sciencemag.org/content/6/19/eaaw1838 https://advances.sciencemag.org/content/6/19/eaaw1838
raiyu 6y ago
I moved from nyc to Miami and actually find the opposite. After three years here there was only one year worse than being in nyc during the summer. The summer almost feels milder here. Anecdotally of course.
magicalhippo 6y ago
It might be >35C as read on a regular thermometer in August in the south of US. However the wet-bulb temperature[1] is, as the name implies, the temperature a thermometer covered in water-soaked cloth. If the water evaporates, it will cool the thermometer down, and as such will read less than a regular (dry-bulb) thermometer. For example, if the dry-bulb temperature is 35C and the relative humidity is 75%, then the wet-bulb temperature would be about 31C[3]. This means the body can still evaporate sweat to cool down, albeit not by much. If you got both a wet-bulb and a dry-bulb thermometer side by side, you can use it to calculate the relative humidity[2]. [1]: https://en.wikipedia.org/wiki/Wet-bulb_temperature https://en.wikipedia.org/wiki/Wet-bulb_temperature [2]: https://en.wikipedia.org/wiki/Hygrometer#Psychrometer_(wet-and-dry-bulb_thermometer) https://en.wikipedia.org/wiki/Hygrometer#Psychrometer_(wet-a... [3]: https://www.psychrometric-calculator.com/HumidAirWeb.aspx https://www.psychrometric-calculator.com/HumidAirWeb.aspx

omosubi 6y ago

I can't find a link right now but I read somewhere that farmers in Costa Rica were starting to get liver damage because the wet bulb temperature had been reached there so we're starting to see the effects already