There are issues with clean water, but that inot the question I am asking. I am asking how chemical processes we use are changing the total amount of water on Earth. Burning hydrocarbons produces water. Making concrete locks the water molecules into hydrated compounds, reducing the amount of water. (Can it be retrieved? Some hydrated compounds can be dehydrated)
I suppose it depends on how precise you want to be.
There’s about 3.66x10[sup]20[/sup] gallons of water in the world, per Google. All of human endeavors have lessened that by less than 0.000000000000% at a round guess.
That seems too low.
World cement production in 2013 was ~4000 million tonnes, or 4e12 kg. 1 kg of cement captures at least 0.42 kg of water, so 1.7e12 kg of water is captured per year. If the total mass of Earth’s water is 1.35e21 kg, then that constitutes 0.000000136% of the total. Small, but that’s a lot few zeroes than you had. Also, that was just one year–if we guess that total human consumption is perhaps 30x of a recent year, then we’re up to 0.000004%.
Of course this ignores the water contribution from hydrocarbons. If my math is right, 3.5e12 m^3 of methane (approximate world use) burns to 2.8e12 kg of water. So it seems that natural gas alone counteracts the capture from concrete. Oil contributes even more.
Yeah, I don’t see how it even comes close. We don’t use anywhere near as much concrete as we do hydrocarbons. In fact, concrete is probably pretty close to steady-state, with new concrete produced to replace old concrete that’s falling apart and eventually re-releasing its hydrogen. Heck, for that matter, it’s basically synthetic limestone, and the powder is produced from natural limestone using basically the reverse process from its setting.
What about biological processes? Photosynthesis in the plants we grow uses water up, while respiration in our own bodies and those of our domestic animals (and plants) releases water.
Yes, but that’s tied to the carbon cycle. As long as (and to the extent that) the carbon cycle is steady-state, so is the creation and destruction of water in respiration and photosynthesis.
Rain from space is constantly increasing the amount of water on the planet also. All of the conversion of water by man seems incredibly trivial compared to the size of the oceans.
Right. That’s why I phrased it “all human endeavors.”
What I don’t have is an estimate of the amount of water locked in solids like hydrates and hydrocarbons. It surely is more than the amount of free water. The mantle is estimated to hold as much water as the oceans. Earth’s Rocks Contain a Hidden Ocean’s Worth of Water Would the earth’s total be a factor of ten? Hard to say.
As a general answer, though, saying that humans have had essentially a 0% effect on the earth as a whole is always the best first guess.
The same kind of qualitative thinking leads some people to believe that humans can’t possibly be affecting the Earth’s climate. Sometimes there’s a hell of a difference between zero and not quite zero. I’d rather people not form an opinion on a subject unless they have a basic grasp of the orders of magnitude involved.
Just wondering about burning hydrocarbons; Weren’t hydrocarbons created by processes (animals and plants) that consumed water and some of it eventually ended up in the hyrdocarbons?
Maybe that’s part of what someone else meant about stability of the carbon cycle?
Is that net or gross water capture ? Keep in mind that much of the raw material (Calcium Carbonate, Aluminates, …) occur in the hydrated form in nature. You have drive water off cement raw materials in the first place to get to cement.
Yes, but that all happened long before humans came on the scene, and much more slowly than they’re being burned now.
That’s a fair point, but it’s not the one I’m making. The qualitative difference is between human effects on the Earth as a whole and upon the surface of the Earth. When people talk about human effects they almost always are thinking of the latter, but don’t frame their question that way. Similarly, your answers pertain to the latter even though I was careful to say “as a whole.”
We can say that humans are affecting the atmosphere, large segments of land, and the upper few meters of the ocean. But humans are not going to wipe life off the earth, or sink continents, or deplete all of any particular resource, or destroy hurricanes or volcanoes by dropping atomic bombs in them. We humans are, to quote the Hulk, puny.
It was a very crude upper bound, assuming that all the input materials were in non-hydrated form. I wasn’t aware inputs were mainly hydrated, so thanks for that. Still, it just reinforces the point that burning hydrocarbons seem to dominate any capture from concrete.
Also, there was an error in my methane calculation. It should be 5.6e12 kg of water production, not 2.8e12. Turns out there’s a difference (almost exactly 2x) between 22.4 and 1000/22.4…
Fair enough. Failing to distinguish between the two cases is also a common element of sloppy thinking among the general public. Affecting the Earth in a way that negatively impacts humanity is a very different proposition than affecting it as a planet.