Say water boiling temperature suddenly became 200°C or even 1000°C, so little evaporation due to boiling would happen naturally on a large scale.

  • What consequences would this have?
  • Would the world be habitable?
  • Would there be any drinking water after it all flows to the sea to remain there?
  • Is there any way to control an artificial water cycle on a large enough scale to act as a natural process?

closed as off-topic by ckersch, bowlturner, Gianluca, T3 H40, Frostfyre Apr 26 '16 at 15:39

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  • "This question does not appear to be about worldbuilding, within the scope defined in the help center." – ckersch, Gianluca, T3 H40
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    $\begingroup$ Remember that for water to be solid, liquid or air, pressure is to be considered too. PV = nRT $\endgroup$ – Kii Dec 4 '15 at 9:28
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    $\begingroup$ Just to be clear, evaporation != boiling point, evaporation starts a 0º C $\endgroup$ – PerroVerd Dec 4 '15 at 10:52
  • $\begingroup$ edited to clarify $\endgroup$ – Ctrl-alt-dlt Dec 4 '15 at 12:52
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    $\begingroup$ @PerroVerd: If you've got pure enough water evaporation can start below 0º C too. Water is weird. $\endgroup$ – Joe Bloggs Dec 4 '15 at 13:13
  • $\begingroup$ everyone would die if there was no water cycle! $\endgroup$ – user20225 Apr 26 '16 at 13:16

This is one of those situations where we all die, but not necessarily in the way you might think.

An important thing to know here is that water evaporation essentially occurs because individual molecules of water get knocked by other molecules in exactly the right way to push them over '100' degrees. This is still going to happen if the boiling temperature is 200 degrees or 1000 degrees, though it will happen a lot less. The world, however, is really big, and contains a lot of water, so rain would still happen and the water cycle would continue.

Not that it helps much. If global humidity dropped by 50% (I'm just pulling that number out of the air, the actual number relies on a lot of other factors such as weather conditions, temperature and distance from the sea) then the resulting drought would kill a lot of crops we rely on, or just kill a lot of people. It would also cause some major climate havoc.

Water vapour is a greenhouse gas. It's not the most long lived greenhouse gas, but it is a powerful one (due to the large amount of it). Strip that away and the temperature of the planet changes drastically, dropping humanity into a nice ice age. Or possibly just counteracting global warming. It's hard to tell with climate science.

However: That isn't your biggest problem. Your biggest problem is that you've changed one of the fundamental properties of a material we rely on to live. Kii noted in the comments (quite helpfully) that the equation PV=nRT is important here (I know it doesn't quite apply as water isn't an ideal gas, but the same principles are important), but instead of it being important on a global scale it's really, really rather important on a cellular one.

Your body has evolved for water to work a certain way at a certain temperature. It's optimised for it, and in the case of semi-permeable membranes (every cell in the body) relies upon the properties of water remaining the same. Our bodies 'know' that water will move in a certain way at 36 degrees. You've just changed the way water works. Suddenly water that was easy to push through the cell wall isn't. Capillaries that were flowing nicely suddenly aren't. The load on the heart changes drastically. Lymph nodes, brain cells, anything that has water in it ceases to function as it used to, leading to massive organ failure likely with the same set of symptoms as hypothermia.

The human race dies, but not because the rain has stopped.

  • $\begingroup$ Nice answer! Do you know if our cells would implode or explode? $\endgroup$ – Kii Dec 4 '15 at 13:06
  • $\begingroup$ Not sure. I think it depends upon exactly what kind of cell it is, what it's currently doing and where it currently is, although I'm pretty confident that in most cases they wouldn't exactly do either. $\endgroup$ – Joe Bloggs Dec 4 '15 at 13:15
  • $\begingroup$ I'm not sure I see how water's boiling point shifting will effect how things work in the body. As far as I'm aware osmosis doesn't rely on the boiling point of water in any way. Similarly the boiling point changing wouldn't change the flow properties of water through our body. Its possible that whatever magic we did to change the boiling point may have changed other properties too but I don't think only the boiling point changing would do what you claim. $\endgroup$ – Chris Dec 4 '15 at 15:48
  • $\begingroup$ Effects on the body I can think of are potentially worse cooling due to sweat evaporation (less evaporation occurs but for each molecule that evaporates it will be taking away more energy) and less water lost through things like exhalation. $\endgroup$ – Chris Dec 4 '15 at 15:51
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    $\begingroup$ @chris It's more that changing the boiling point must change the other properties of the water, and if all the water in our bodies suddenly starts acting like it's at 18 degrees (we halved the gradient of viscosity vs temperature) then we'll have similar effects to hypothermia. Good point on the cooling failures and lack of exhaled water though. We can add drowning to the potential ways this can kill us! :D $\endgroup$ – Joe Bloggs Dec 4 '15 at 16:53

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