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In my setting, one of the habitable (?) worlds has a global average temperature of 34 degrees Celsius (93.2 F). Is this within the human habitability range, or is it too hot?

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    $\begingroup$ Just something that is worth keeping in mind: It's usually a good idea to wait at least a few hours before accepting an answer. Questions with accepted answers tend to get less attention from the community, so accepting an answer early actually reduces your chances of getting an even better answer. Now, if you are happy with JetStream's answer then it is certainly well within your rights to accept it, but I would generally encourage waiting up to a day (to allow for people in different time zones) before accepting an answer. You can still obviously vote up answers that you find useful. $\endgroup$ – a CVn Jul 8 '16 at 11:41
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    $\begingroup$ As jknappen noted in an answer (should have been a comment) this question is not really well-posed; it can't be answered based only on average. The answer you accepted is also over-simplified. $\endgroup$ – R.. Jul 8 '16 at 15:08
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    $\begingroup$ If you were to include the standard deviation, or at least some sort of min/max range combined with distribution of how much of the planet falls into each range, you might get more detailed answers. $\endgroup$ – Mwr247 Jul 8 '16 at 15:19
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    $\begingroup$ Also the world is not really described or defined. For instance, I envision it as 'habitable' due to the tens of thousands air-conditioned 'mega-plexes' where people live and work. So when people rarely, if ever, need to venture outside that global ave temp is not much a concern. $\endgroup$ – JoeG Jul 8 '16 at 17:08
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    $\begingroup$ You're missing a critical factor: Humidity. 93.2F and 0% humidity is mildly unpleasant. (There's a reason those of us in dry climates say it's a dry heat--it makes a big difference!) 93.2F and 100% humidity is at the very edge of survival and would require living several feet underground and only venturing out at night--and if there were substantial seasonal variation you would need to be deeper still and have long connections between your house and the surface. $\endgroup$ – Loren Pechtel Jul 9 '16 at 4:16
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We can live in this temperature. We would have to adapt to it but we will get used to it soon.

The limit for living on a planet is the point that proteins denature (~40 degrees Celsius). Because at this point we (our body) could no longer survive.

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  • $\begingroup$ Thanks! I was really hoping I hadn't screwed up something big-time. $\endgroup$ – Alexader Ferguson Jul 8 '16 at 11:38
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    $\begingroup$ Problem is, if the average temperature is 34ºC, there will be plenty days and places when and where it will go far above 40ºC. But as anyone who lives in Rio de Janeiro knows, we can easily survive environmental temperatures above 40ºC. We only die if our own body (and not just our skin!) goes too much above 40ºC for too much time. $\endgroup$ – Luís Henrique Jul 8 '16 at 12:33
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    $\begingroup$ I think the limit is significantly below 40°C; without active cooling of some sort, you need an ambient temperature that can keep the body below 40°C while it's constantly producing heat. Also, while sustained life for the current generation may be possible, reproduction will likely not be possible at such temperatures due to the effects of temperature on sperm production. $\endgroup$ – R.. Jul 8 '16 at 15:06
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    $\begingroup$ According to an old teacher of mine, human beings can handle high temperatures (35-45º) during the day for as long as the nights are significantly cooler. This was years ago, so I can't really recall details. $\endgroup$ – Sara Costa Jul 8 '16 at 15:58
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    $\begingroup$ The limit is actually higher than that: the human body has an active cooling system that can produce temperatures below ambient. The temperature limit is around a heat index of 54ºC (source: my research for answering another question), though as temperatures approach that, your ability to do anything but lie around trying not to overheat rapidly declines. $\endgroup$ – Mark Jul 9 '16 at 0:21
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The average temperature of Earth is ~15 degrees Celsius. So, your planet is about 19 degrees warmer than Earth. I suppose Dakkar would be uninhabitable if it were 19 degrees warmer, but Helsinki would have a temperature similar to Miami. Seems livable to me, though if its life forms were autochtonous, life in each hemisphere would probably differ a lot from the other side.

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  • $\begingroup$ The average temperature of Earth is ~15Should now officially be updated to 16℃. $\endgroup$ – user2284570 Aug 28 '16 at 9:59
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A global average temperature of 34°C would be very uncomfortable and have expanses of areas uninhabitable by humans, but it would not preclude human life in some areas. The bigger problem would be understanding wet-bulb temperature. In a civilization with advanced technology, interior areas could be made habitable, but there is a limit where it becomes impossible to survive in the unprotected environment, even if not working/moving.

For that limit, the humidity of the environment influences the ability for living organisms to radiate the heat that they produce. From this article on the impact of temperature and climate change on survivability:

The wet-bulb temperature is probably not a very good predictor of the "feels-like" temperature for most common conditions, which is why it is not used for this. However, it can be used to establish an absolute limit on metabolic heat transfer that is based on physical laws rather than the extrapolation of empirical approximations. That is why we focused on it instead of the usual measures.

So, more parameters are required to understand how survivable your world is to humans.

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  • $\begingroup$ Nice post and Welcome to Worldbuilding! $\endgroup$ – CrazySlayaNinjaBear Jul 9 '16 at 4:45
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Life on Earth lives in a delicate balance. The rise of only a few degrees C would spell absolute disaster if it happened here. On Earth, the average temperature is slightly less than 15 C (58.3 F). This means that the average temperature on this planet would be roughly 50% hotter. Over the past several decades, Earth's average temperature has risen only about a degree Celsius, but that small change has had a huge impact on weather patterns, as well as the melting of glaciers, and polar ice caps.

If the average global temperature is 34 C (93.2 F), then you would have to take into account that the temperature extremes would fluctuate much more than they do on Earth. A rise to 34 C would effectively wipe out most of life on Earth. Surface water would evaporate, and leave giant inland deserts. Storms would also be so massive, that we currently have no means of classifying them.

It may be possible for a few pockets of life to survive, but the vast majority of the world would be a wasteland. The seas levels would also rise significantly, and low coastal areas would be completely underwater. People could survive there only in underground habitats, or possibly at the poles.

The tropical regions would be completely scorched. Temperatures would exceed 70 C. The ground would be completely dry and parched. The clay would become rock hard, and there would not be any signs of life.

Civilization would be incredibly insular. Since the people would not be able to travel far enough to visit other colonies. The biggest extreme would be people living at opposite poles. Their culture would evolve completely separately from each other, and they would not share a language. The people would also be adapted to the heat.

In conclusion, 34 C is most likely too extreme for humans to prosper. There may be some individuals alive, but there would be a lack of resources, and especially food. It would be far more believable if the temperature was lower. Even 5 C higher on Earth would be pretty extreme.

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    $\begingroup$ "This means that the average temperature on this planet would be roughly 50% hotter". The average temperature would increase from 288K to 307K, so just ~7%. $\endgroup$ – JonathanReez Jul 8 '16 at 17:33
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    $\begingroup$ The world would be much more than 7% hotter since 34 is just the average. I'm not sure how accurate the 50% is, but the increased temperature would put the planet slightly outside of the "Goldilocks Zone" regardless of that figure. $\endgroup$ – Jason Hutchinson Jul 8 '16 at 18:05
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    $\begingroup$ "The rise of only a few degrees C would spell absolute disaster if it happened here" this isn't quite accurate. While I agree that global warming is bad for our current situation, it's important to realize that the context of this question is whether humans would be able to survive. The reason that our planet changing is problematic is not because we won't continue to live, but because so many of the current species would have to adapt. Such imbalences have significant consequences. If the planet was already consistent at the higher temp, life would already have adapted. $\endgroup$ – zzzzBov Jul 8 '16 at 18:31
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    $\begingroup$ If the current average is 59°F = 15°C = 288°K adding 50% gives you 432°K = 159°C = 318°F. With an average temperature well above boiling, I doubt that there would be any habitable areas even in the coolest parts of the planet. Think Venus. When you multiply temperatures you have to calculate it from absolute zero, not the arbitrary zeros that exist in both Celsius and Fahrenheit. The OP's world is not Earth. He specifically says one of the habitable worlds. $\endgroup$ – CJ Dennis Jul 9 '16 at 0:32
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    $\begingroup$ A planet with a 34ºC average temperature would probably be in a delicate balance, too, just a different delicate balance. A world that is not balanced is quite certainly uninhabitable; so you are right in that the Earth would be uninhabitable if its temperature increased 19 degrees. But a planet that is already at equilibrim at 34º can quite probably be settled by humans. $\endgroup$ – Luís Henrique Jul 9 '16 at 13:12

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