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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." - 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.
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!
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!
According to my calculations, 1.8 mm per year means about 3.5 inches in the 50 years they're talking about. They're not laughing in the Maldives, Florida or a number of low-lying coastal regions, such as, oh, yeah, Manhattan.
I have a hard time picturing how a hover dam manages to trap any water. Won't the water simply flow underneath the dam?
Except no one looks back at the 20th century and remembers the great sea level disaster. The sea rose 7" over the 20th century, with zero acceleration in rate until the satellites came online, and no one noticed for 90 years. (Which obviously proves satellites cause sea level rise. )
If you continue to just use the geologically stable tide gauges (as was used before satellite data became available) the rate of sea level change hasn't changed in 100 years.
The sea rose 7" over the 20th century, with zero acceleration in rate until the satellites came online, and no one noticed for 90 years. (Which obviously proves satellites cause sea level rise. )
So the Chinese are the good guys for blowing up satellites after all.
... time to put those beavers to work!
Must ... resist ... obvious ... joke
I am officially gone from
...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."
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.
Coral Atolls cannot suffer from sea level rise, they are the result of life living near the surface creating a deposit that itself builds the atoll. The Maldives will never suffer from gradual sea level rise. Charles Darwin himself discovered how Atolls remain above water. If these islands were bedrock, you might be right, but they're not. Atolls are essentially floating islands.
http://www.pacificdisaster.net/pdnadmin/data/original/The_dynamic_response.pdf
I swear they give me mod points to shut me up.
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?
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.
Well, there is one particular satellite that has been well known to cause sea levels to rise quite significantly, so I think you might be on to something here...
Of course nobody reads the FAQ! If people read the FAQ, the Questions wouldn't be so Frequently Asked.
Well, there is one particular satellite that has been well known to cause sea levels to rise quite significantly, so I think you might be on to something here...
Well, yes, but not globally.
"None can love freedom heartily, but good men; the rest love not freedom, but license." --John Milton
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
You aren't very polite, and you aren't good at doing basic research. If you'd spent five minutes on Google, you might have found this, which shows a change in the coastline of more than .5 meters over the last 146 years.
If you can't tell what continental drift and erosion has to do with sea-level rise, I don't know what to tell you. Continental drift means some coasts are growing an order of magnitude larger than the sea change. In other places, it is shrinking many times faster than sea level change.
Thus we see, for people who live on the coast, sea level rise of 1.8mm is a laughably small problem, when compared to the many other things they are facing.
"First they came for the slanderers and i said nothing."
Except no one looks back at the 20th century and remembers the great sea level disaster.
Ever hear of Venice? Of course Venice is also subsiding, but seven inches on top of that has made a big difference to them.
The problem with sea level rise in the short term isn't that suddenly you're city is drowned every day of the year. It's with the increase in frequency with which rare catastrophic events occur. Every coastal city has a high water level below which flooding effects are marginal and above which they are catastrophic (e.g. a levee is overtopped). How close waters commonly come to that mark determines the impact of a marginal increase in sea level.
Cities like Venice or New Orleans which are already prone to flooding are certainly affected by an 18 cm rise in mean sea level, although that effect isn't necessarily seen every year. Boston on the other hand was built to withstand 3-4m tides and has never had a major flood from the sea, so the 18 cm rise in the 20th C. had zero effect on it. If at some point in the future sea levels rise by a meter or so, flooding might become a common event in Boston. At that point a further 18 a cm rise would be very expensive to deal with.
The effect of sea level rise is not linear, and it's not uniform throughout the world. The effect depends on how a city is constructed and situated.
Now as to "geologically stable tide guages", if you knew anything about surveying you'd know that rather begs the question. In any case you can get any result you want by arbitrarily throwing out data; *mocking* data you'd prefer not to exist doesn't count as an argument.
Post may contain irony: discontinue use if experiencing mood swings, nausea or elevated blood pressure.
They're not laughing in the Maldives
Actually, they are lauging. Sea level in the Maldives actually went down, but they really love the attention and money they can get from claiming that they're drowning.
An acre-foot of water is one acre of area covered by a foot of water. It is a common unit in the United States for measuring large volumes of water. One acre-foot is equal to 1233.48184 cubic meters or 325851.4 US gallons. Hogsheads vary is size but if you take it to be 63 gallons then an acre-foot is about 5,172 hogsheads. Troy ounces is a measure of mass, not volume.
Perfectly "clean" rainwater should have a pH close to 7.0 -- being pure water. 5.6 is bordering on "acid rain". (I'll check my rainwater sisterns, but they've had a long time to settle.)
Yes, sea water is highly buffered. However, that buffer is not instant. Look at the small scale in my (freshwater) aquariums... they have carbonate buffers in there (a lot of it, in fact -- aragonite and commerical buffers) and the pH can still dip below 6.6. If I draw a sample for testing, sealed in the tube, the pH will slowly recover to 8.4 as the disolved buffer does it's job. A great deal of the buffer capacity of the oceans are the coral in them.
But yes, I agree, CO2 is not what's going to destroy our oceans. We've been doing far, far worse things to them for a long time now.