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Human Water Use Accounts For 42% of Recent Sea Level Rise
scibri writes "During the latter half of the twentieth century, global sea level rose by about 1.8 millimeters per year. The combined contribution from heating of the oceans, which makes the water expand, along with melting of ice caps and glaciers, is estimated to be 1.1 millimeters per year, which left some 0.7 millimeters per year unaccounted for. It seems that the effects of human water use on land could fill that gap. Researchers report in Nature Geoscience that land-based water storage could account for 0.77 millimeters per year, or 42%, of the observed sea-level rise between 1961 and 2003. The extraction of groundwater for irrigation and home and industrial use, with subsequent run-off to rivers and eventually to the oceans, represents the bulk of the contribution. It would be even worse if we weren't also locking up lots of water from rivers behind dams like the Hoover Dam."
It would be even worse if we weren't also locking up lots of water from rivers behind dams like the Hoover Dam
Even worse? Like a couple more millimeters! Evacuate NYC!
"It would be even worse if we weren't also locking up lots of water from rivers behind dams like the Hoover Dam." - Isn't the rate at which it leaves the lake the same as if the dam hadn't been there (with maybe the exception of evaporation...), just with a delay? My understanding was that dams affect latency but not throughput...
The sea levels have been rising since the last ice age, and for much of that time much faster than now. The volume of the ocean changes for many reasons. Those lands that are essentially at sea level are doomed anyway, no point in the sob stories of displaced natives as their land would be covered even without any alleged actions by man, if not now then in next few centuries. Better they move now before their population grows even bigger and more people are affected.
So we just need more dams to fix this right, time to put those beavers to work!
the 'Anthropocene', we have changed the surface of the earth so much.
This is obviously just another cry of "the sky is falling" from a bunch of alarmists pushing their anti-freedom agenda.
There's no credible evidence that this so-called "ground water" exists at all. Look down at your feet: The ground is made out of dirt. How do they supposedly turn all this dirt into water? Answer: They can't. Dirt is black, water is clear. You don't get one from the other. It's just common sense, people.
There's nothing to see here. Move along.
So how long can we use surface water at this rate before we run out?
Give me Classic Slashdot or give me death!
I have a hard time picturing how a hover dam manages to trap any water. Won't the water simply flow underneath the dam?
...by this comment at the end of the summary?
It would be even worse if we weren't also locking up lots of water from rivers behind dams like the Hoover Dam.
I don't see why this matters much. If you released all of the dammed water, you'd have a one-time increase in ocean levels. So what? Dams control rivers, sure, but those rivers are still flowing and have been this entire time. Surely the throughput from that river over a relatively short period of time is far more significant than any amount of water dammed along that river.
To me, that statement is as silly as, "We'd have even more cars on the road if we weren't locking some of them up at red lights and intersections."
How is this news for nerds? Hell, there is probably a good percent of the slash dot crowd that doesn't even bathe regularly... Really, the alarm over AGW is really not tech related unless any of the following: Its a _real_ crisis (just one little drowning?), 2. something that can be done, 3. or it is actually interesting in a nerdy kind of way...
If this were a real concern, beachfront property prices would be falling. Islands would be littered with For Sale signs. 1 mm over many decades doesn't mean squat..
We should scoop up millions of gallons of seawater and blast it into space. Water on the moon, indeed!
There are other causes besides just melting ice caps and expanding water and man made activities. For instance, the Great Lakes in the US are rising. As they rise, the more and more water runs out of them and eventually finds its way to the sea. There are other large bodies of water with similar geological forces in play that have nothing to do with man's activity.
It seems like places like Venice were worried about rising water levels long before 20th century man started irrigated cropland and the like. I am not a climatologist or anything like that but it seems like an awfully simple model that only looks at melting ice, warming water and the rest is because of people.
The oceans are also much deeper than a few millimeters. Total volume isn't really meaningful here.
One millimeter across the world's oceans is about 350 cubic kilometers. So if the contents of the Hoover Dam flowed to the ocean, they would (ostensibly) raise the sea level by ~0.1 mm.
It would be even worse if we weren't also locking up lots of water from rivers behind dams like the Hoover Dam.
How would that be? Dams don't make the water go away. Over time, the amount of water going into the reservoir equals the amount leaving, or else the water levels would either drop or overflow the dam. The only significant change I'd see is that dams increase the surface area of the water and would therefore raise evaporation, so some of the water that would normally go downstream would turn into atmospheric moisture instead. For global warming purposes, that's probably not a good thing. But would it actually have a non-negligible effect on ocean levels?
Dewey, what part of this looks like authorities should be involved?
It's called Post-Glacial Rebound, the land was pushed down by the glaciers, it's still rising now that the ice is gone. And since water runs down hill the Great Lakes (among others) are draining.
I'm pretty sure he was saying that it always continues warming from one ice age until we hit the next. Whether we melt all the ice a hundred years sooner is unimportant in both the short and long term. In the medium term you have a bunch of people pissing and moaning because they got stuck with the changing real estate rather than their great-grandkids.
The ice is going to melt. We are going to have another ice age. There's not a damned thing anyone can do about it and it's probably not going to happen in my lifetime, so why should I give a fuck?
Violence is like duct tape. If it doesn't solve the problem, you didn't use enough.
it is called "averaging". If you have a hole year to do it, you can do a fucking lot of it.
10 ?"Hello World" life was simple then
The older method, still in use, is to use tide gauges. Basically, these are long cylinders placed below the water level, and thus are able to remain mostly unaffected by waves. Hundreds, if not thousands of measurements are taken electronically every day, and these measurements give a good measure of the water level at that location over the course of the year. According to Wikipedia, there are over 1700 tide gauges being used worldwide, so you wind up getting a good average of the worldwide sea level.
The newer method is to use satellite altimeters which use radar to give accurate measures of the altitude of the land or sea below them.
The two methods combined give millions of data points over the course of a year, and scientists have been taking measurements since the mid-1800's.
Despite what one may think, it's not quite like there are scientists on beaches around the world placing a new toothpick in the sand for each and every wave.
http://www.telegraph.co.uk/comment/columnists/christopherbooker/5067351/Rise-of-sea-levels-is-the-greatest-lie-ever-told.html
But hey, we all know that "there is 100% consensus among the serious scientists on AGW", right?
-Styopa
Old fashioned tidal gauges are very acurate if kept well maintained, a simple tube effectively removes the waves, larger ones use what is called a "stilling well" but the principle is the same as measureing the 'true' hieght of choppy bath water with a perspex tube. Having said that I'm pretty sure the 0.77mm/yr is a statistic, ie: the gradient of the trend over a number of decades or centuries in some areas. An (unexplained) three inch rise over 100yrs is certainly something that could be observed in historical records.
I don't know if these guys are right or wrong, so I cheated a bit by skimming TFA, the source is credible and previous research backs the general conclusion. I still don't know if they are right but either way it is nice to see a slashdot article that highlights a genuine conundrum in Earth science.
And did you exchange a walk on part in the war for a lead role in a cage? - Pink Floyd.
With all the earthquakes that happen undersea every year, the is some major ocean fllor remodeling going on. Of course the zero sum model that they are pushing also must mean that the ocean volume change because of tectonic shift is also zero sum.
A few thousand square mles of ocean floor raising a couple inches will have more of effect to sea level increases than all man made activity over the last ten thousand years.
I'm suprised that they haven't blamed hunting beavers in the 1700's for an increase in sea level changes because all the beaver dams that would have been built would have prevented ONE TRILLION (pinky to upper lip) gallons of water from entering the sea.
Actually, I know that 1 of the great lakes (forget the one) is lower and the amount is approximately the amount taken out of it for freshwater use (farming is always a big water user.) I heard about the studies back when the Great Lake states were discussing a deal where they would forbid any other state from stealing water from the Lakes - which sounded a bit nuts to people up here but people in AZ just assume someday they'll get water from the Great Lakes like we were just next door. I followed the hardly covered issue back then because having been in AZ, I know it was not crazy to the people wanting to make the deal. Thankfully our politicians opposed it (no lobby or media coverage) but when the time comes they'll easily change positions and undo past law if properly bribed.
Actually, the whole region around the Great Lakes is rising. It was compressed during the last iceage and has be returning to it's normal, decompressed state ever since. If it was simply water being taken out of the lakes for other use, then the level would be low everywhere. However, the one end has raised significantly (in geological terms) and has nothing to do with water usage. However, the water that was in the now lifted area has run out, ultimately into the ocean (through the normal channels).
Other parts of Canada and the northern Midwest are also experiencing the lifting/tilting. They just don't have massive bodies of fresh water on top of them so it isn't noticeable like it is on a shoreline.