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posted by martyb on Sunday March 14 2021, @12:29AM   Printer-friendly

Global heating pushes tropical regions towards limits of human livability:

Humans’ ability to regulate their body heat is dependent upon the temperature and humidity of the surrounding air. We have a core body temperature that stays relatively stable at 37C (98.6F), while our skin is cooler to allow heat to flow away from the inner body. But should the wet-bulb temperature – a measure of air temperature and humidity – pass 35C, high skin temperature means the body is unable to cool itself, with potentially deadly consequences.

“If it is too humid our bodies can’t cool off by evaporating sweat – this is why humidity is important when we consider livability in a hot place,” said Yi Zhang, a Princeton University researcher who led the new study, published in Nature Geoscience. “High body core temperatures are dangerous or even lethal.”

The research team looked at various historical data and simulations to determine how wet-bulb temperature extremes will change as the planet continues to heat up, discovering that these extremes in the tropics increase at around the same rate as the tropical mean temperature.

[...] Dangerous conditions in the tropics will unfold even before the 1.5C threshold, however, with the paper warning that 1C of extreme wet-bulb temperature increase “could have adverse health impact equivalent to that of several degrees of temperature increase”. The world has already warmed by around 1.1C on average due to human activity and although governments vowed in the Paris climate agreement to hold temperatures to 1.5C, scientists have warned this limit could be breached within a decade.

This has potentially dire implications for a huge swathe of humanity. Around 40% of the world’s population currently lives in tropical countries, with this proportion set to expand to half of the global population by 2050 due to the large proportion of young people in region. The Princeton research was centered on latitudes found between 20 degrees north, a line that cuts through Mexico, Libya and India, to 20 degrees south, which goes through Brazil, Madagascar and the northern reaches of Australia.

Journal Reference:
Yi Zhang, Isaac Held, Stephan Fueglistaler. Projections of tropical heat stress constrained by atmospheric dynamics, Nature Geoscience (DOI: 10.1038/s41561-021-00695-3)


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  • (Score: 2, Insightful) by Anonymous Coward on Sunday March 14 2021, @10:15AM (5 children)

    by Anonymous Coward on Sunday March 14 2021, @10:15AM (#1123966)

    Pretty much everywhere near the equator regularly sees longterm temperatures at 38, many well into the 40s. And this has been true for centuries. And people are just fine.

    What's next, humans will immediately keel over dead at 500ppm CO2? Check your indoor CO2 levels sometime, if you don't get the "joke".

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  • (Score: 0) by Anonymous Coward on Sunday March 14 2021, @03:37PM (4 children)

    by Anonymous Coward on Sunday March 14 2021, @03:37PM (#1124034)

    Ribbet. That's the sound of a slowly boiling frog.

    • (Score: 1, Touché) by Anonymous Coward on Sunday March 14 2021, @04:11PM

      by Anonymous Coward on Sunday March 14 2021, @04:11PM (#1124060)

      Buy carbon credits. That's the sound of a quickly enriching Al Gore.

    • (Score: 1, Interesting) by Anonymous Coward on Sunday March 14 2021, @04:45PM (2 children)

      by Anonymous Coward on Sunday March 14 2021, @04:45PM (#1124077)

      That makes no sense. These places get *way* above the temperatures mentioned in this article implied to be deadly and life gets on 100% fine, even during the hot part of the day/year. For instance here [timeanddate.com] is the 14 day weather forecast for Bamako, the capital of Mali. Every single day next week (and for the coming weeks) will be hitting into the 40s. And it's not going to get cooler anytime soon there. And life will go on. And this has been the case for decades and even centuries.

      This paper is effectively claiming that the normal temperatures billions of people endure on a yearly basis are somehow now suddenly dead. Granted heat stroke does exist, as does hypothermia, but these are generally from more vulnerable populations or people engaged in really stupid behavior. A healthy person can happily go on a hike or a run in 40+ degree temps and be just fine, though you obv want to bring some water with you.

      And one interesting aside that I chose not to be a dick about: that old metaphor is very useful, but actually fake. Frogs will jump out of water gradually heated to a boil long before there's any risk to their health.

      • (Score: 2) by PartTimeZombie on Sunday March 14 2021, @11:53PM (1 child)

        by PartTimeZombie (4827) on Sunday March 14 2021, @11:53PM (#1124198)

        This paper is effectively claiming that the normal temperatures billions of people endure on a yearly basis are somehow now suddenly dead.

        No-one is claiming that. [wikipedia.org]

        Bamako Extended Forecast with high and low temperatures

        Feels Like:35 °C
        Humidity:9%
        Precipitation: Rain: 0mm Snow: 0mm
        Precipitation Chance: 1%

        • (Score: 0) by Anonymous Coward on Monday March 15 2021, @07:03AM

          by Anonymous Coward on Monday March 15 2021, @07:03AM (#1124339)

          The temperatures are down a substantial amount from when I posted since a storm is now coming in. Such is the nature of dynamic pages. Here [archive.org] is some rando archive from Bamako during the summer. Including extreme days like:

          Feels like: 58°C (converted by me from 136°F)
          Humidity: 52%

          And from your link, "The theoretical limit to human survival for more than a few hours in the shade, even with unlimited water, is 35 °C (95 °F)." Again, this makes no sense whatsoever. That, or we're talking about baseline temperatures that even Mali isn't getting to which are going to be base temperatures in that what, the 50s? Which not even the most off their rocker alarmists are proposing.