How Hot Until We Cannot Survive on Earth?

Have you ever thought about the very narrow band of environmental balance required to sustain life on this planet?  In the vast extremes of the cosmos, it’s a pretty narrow band.  We require a very specific mixture of oxygen in the air we breathe.  We require a very specific diet which luckily is readily available on this planet.  We require a specific amount of sleep each day, which coincidently is about the same amount of time we spend in darkness during single rotation of the Earth.  And we require a very specific range of temperature, warm enough to avoid hypothermia and cool enough to avoid heat stroke.

It’s amazing that life can even exist.  I find it hard to believe that this is all just random coincidence, but that’s a debate for another day.  Today, I learned the answer to one of my questions about this narrow band of balance we live in.  How hot can it get before we can no longer sustain human life on this planet? With all the global warming hoo-haa flittering about the news media, it would seem a rather important question.  Well, some fine professors at Purdue University looked into the matter and came up with some interesting observations.

It turns out, however, that the answer isn’t exactly straight forward as I expected.  I mean it is and it isn’t.  They do give us a temperature rise in which 50% of the world’s population would be uninhabitable.  To be clear they are not giving us a temperature, but rather a measure of the rise in temperature above our current levels.  (Yeah… seems like science is never as easy to understand as one would hope.)  Here is what they found according to Matthew Huber, Purdue professor of earth and atmospheric sciences.

“We found that a warming of 12 degrees Fahrenheit would cause some areas of the world to surpass the wet-bulb temperature limit, and a 21-degree warming would put half of the world’s population in an uninhabitable environment.”

So basically an increase in temperature of 21 degrees Fahrenheit (12 degrees for the Celsius crowd) would mean that half of us would have to start looking for a new place to live.

This study, and the quote above, mention wet-bulb temperature, which is actually a very interesting unit of measure.  It turns out that a change in temperature alone is not the only factor in human survivability.  Humidity is actually a huge factor in how sustainable life is in higher temperatures.  I live in Florida, so believe me, I know humidity.  Humidity is the reason the weather person invented the “feels like” index, when he/she says it’s 95 but it feels like 110.  Welcome to summer in Florida.  This wet bulb temperature is a way of combining humidity and temperature into a single measurement.

Steven Sherwood, a professor at the Climate Change Research Centre at the University of New South Wales, Australia, says “prolonged wet-bulb temperatures above 95 degrees would be intolerable after a matter of hours.” He further described it like this:

“The wet-bulb limit is basically the point at which one would overheat even if they were naked in the shade, soaking wet and standing in front of a large fan”

Funny, I’ve never heard American professors talk about standing naked in front of fans.  Anyway, humidity goes hand in hand with temperature as far as human survivability is concerned.  High humidity and high temperature reduces the ability to cool your body.  Essentially, at some point of high heat and high humidity, we lose the ability to keep cool, and we die in a smoldering pile.  And if you’re in the 50% of the world that already experiences high heat and high humidity, that number is somewhere around 21 degrees hotter than you are currently experiencing.  When I see the thermometer on my back porch hit 120, I’m packing it up and heading for the Arctic.  Alaska will be the new cool place to live (bad pun.)

Tagged as: Knowledge