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."

Comments

Worse?

[Anonymous Coward]

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!

Re:Worse?

[jdgeorge]

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.

Re:Worse?

[phantomfive]

Don't forget geological effects. Continental drift can be as much as 50mm a year. Then you have places like this, where the annual change is measured in feet, not millimeters.

When it comes to coastal issues, a 3.5 inch sea rise in 50 years is relatively small.

Re:Worse?

[TheSeventh]

That article you linked to is about coastal erosion, where the soil holding up the cliff was washed away into the sea. What does this have to do with sea rise or anything else? And it wasn't talking about the 'annual change' of that particular coastline, but the fact that several feet of the ground between a particular apartment building and the ocean was washed away in a few days.

Instead of being modded insightful, you should be modded Off-topic instead.

Re:Worse?

[phantomfive]

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.

Re:Worse?

[hey!]

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.

Re:Worse?

[TheSeventh]

Coward. This was disproven, but why bother with facts, when you can't even spell?

They especially love the attention they get from Tsunamis, like the one in 2004 that wiped out quite a few of their islands. 57 islands were seriously damaged, 21 resort islands had to be closed, 6 were destroyed, and 14 had to be completely evacuated. Only 9 of over 1300 received no damage.

With an average ground height of less than 5 feet above sea level, I'm sure they'll be fine for at least a few more years.

Re:Worse?

[JWSmythe]

    I still haven't figured out how everything on television, even educational channels like History, have become tabloid television. It feels like I can get more reliable information from the Weekly World News, and The Onion.

    You get real news from Comedy Central.

    You get blatant lies and propaganda from Fox News.

    You get sensationalized half truth from every other "news" outlet.

    You get wild ass conspiracies and paranormal BS from Discovery, History, and National Geographic.

    No wonder people seem so dumb. They aren't actually idiots, they've just been exposed to so much "crap as fact" media, that they don't know any better.

    BTW, you're thinking of von DÃniken, not Vonnegut.

Really?

[Dmritard96]

"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...

Re:Really?

[TapeCutter]

They claim the ocean is rising due to increased runoff from human activity, yet it's well known that most of the worlds major rivers are a shadow of their natural self by time they reach the ocean (if they get there at all). Perhaps stormwater drains are taking up the slack, but for the moment I'm left with two credible claims that on the surface appear to directly contradict each other?

That's why geologists now call this epoch

[fredrated]

the 'Anthropocene', we have changed the surface of the earth so much.

The relevant part

[Corson]

The relevant part in this shocking news is "0.77 millimeters per year", not "42% of recent sea level rise". How on earth does one measure 0.77 mm per year? When I watch the waves breaking against the sea shore this seems so far fetched.

Hoover dam

[spectrokid]

Ok, smartasses: the Hoover dam contains 37 cubic kilometer of water. The oceans 1.3 BILLION. This argument is ridiculous.

Anyone else confused?

[Anubis IV]

...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."

More news for AGW alarmists

[bhlowe]

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..

Could be other causes, too

[Dcnjoe60]

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.

Re:sea levels rising for thousands of years

[Penguinisto]

re. Outer Banks: I don't think you'd lose their buffer characteristics overnight; you'd have to wait until they were under something like 30' of ocean. They're still there and able to temper/stop any storm surge from hurricanes.

re. aquifers: why would you want to pump it anywhere? You fill the aquifer with the water that is still uphill by damming it up while it's up there - it's less energy-intensive that way. Problem is (if Oregon is any indication), building a dam is politically impossible these days.

re: ground water: A big problem is that some aquifers (e.g. the Ogallala) span multiple states. Who gets to pay for, manage, and regulate that?

One more bit: In most of the Western US, water is a very touchy subject. Water rights and ownership is separate from property and mineral rights (e.g. you can often own the dirt, but not the water to be found in, under, or on it). Except for parts of Oregon and Washington, you will find water rights, ownership, and laws to be a byzantine and brain-hurting mess to sort through. That it works at all without physical violence breaking out is a miracle.

How?

[Just Some Guy]

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?

Re:sea level rise has been a lie/scam anyway.

[Overzeetop]

"Despite fluctuations down as well as up, "the sea is not rising," he says. "It hasn't risen in 50 years." If there is any rise this century it will "not be more than 10cm (four inches), with an uncertainty of plus or minus 10cm".

So...he's basically saying that he has a mean rise somewhere just shy of 10cm, and an uncertainty of 10cm. That would, to a simple engineer like myself, suggest that sea levels ARE rising, and that they are rising at a rate which is somewhere between a negligible amount and 20cm over 100 years, or (wait for it) 2mm per year. TFS suggests that 1.8mm/yr is the annual average amount for the last fifty years. Presuming that there was no change - or a negligible one - from 1910-1960, that would average out to 0.9mm.yr.

That's 9cm in 100 years or 10% less than Dr MÃrner's "not more than" mean, and well within his +/- 10cm. band.